diff --git a/lib/action/sfAction.class.php b/lib/action/sfAction.class.php
index f796cd30d..14b0223d4 100644
--- a/lib/action/sfAction.class.php
+++ b/lib/action/sfAction.class.php
@@ -404,7 +404,7 @@ public function setSecurityConfiguration($security)
    */
   public function getSecurityValue($name, $default = null)
   {
-    $actionName = strtolower($this->getActionName());
+    $actionName = strtolower((string) $this->getActionName());
 
     if (isset($this->security[$actionName][$name]))
     {
@@ -517,7 +517,7 @@ public function getLayout()
    */
   public function setViewClass($class)
   {
-    sfConfig::set('mod_'.strtolower($this->getModuleName()).'_view_class', $class);
+    sfConfig::set('mod_'.strtolower((string) $this->getModuleName()).'_view_class', $class);
   }
 
   /**
diff --git a/lib/autoload/sfAutoload.class.php b/lib/autoload/sfAutoload.class.php
index 5f68f8039..982822ca4 100644
--- a/lib/autoload/sfAutoload.class.php
+++ b/lib/autoload/sfAutoload.class.php
@@ -83,7 +83,7 @@ static public function unregister()
    */
   public function setClassPath($class, $path)
   {
-    $class = strtolower($class);
+    $class = strtolower((string) $class);
 
     $this->overriden[$class] = $path;
 
@@ -99,7 +99,7 @@ public function setClassPath($class, $path)
    */
   public function getClassPath($class)
   {
-    $class = strtolower($class);
+    $class = strtolower((string) $class);
 
     return isset($this->classes[$class]) ? $this->classes[$class] : null;
   }
@@ -185,7 +185,7 @@ public function autoload($class)
    */
   public function loadClass($class)
   {
-    $class = strtolower($class);
+    $class = strtolower((string) $class);
 
     // class already exists
     if (class_exists($class, false) || interface_exists($class, false) || (function_exists('trait_exists') && trait_exists($class, false)))
diff --git a/lib/autoload/sfCoreAutoload.class.php b/lib/autoload/sfCoreAutoload.class.php
index ff6dfce1b..c92e9ba89 100755
--- a/lib/autoload/sfCoreAutoload.class.php
+++ b/lib/autoload/sfCoreAutoload.class.php
@@ -116,7 +116,7 @@ public function autoload($class)
    */
   public function getClassPath($class)
   {
-    $class = strtolower($class);
+    $class = strtolower((string) $class);
 
     if (!isset($this->classes[$class]))
     {
@@ -169,7 +169,7 @@ static public function make()
           || false !== stripos($contents, 'interface '.$class)
           || false !== stripos($contents, 'trait '.$class))
       {
-        $classes .= sprintf("    '%s' => '%s',\n", strtolower($class), substr(str_replace($libDir, '', $file), 1));
+        $classes .= sprintf("    '%s' => '%s',\n", strtolower((string) $class), substr(str_replace($libDir, '', $file), 1));
       }
     }
 
diff --git a/lib/autoload/sfSimpleAutoload.class.php b/lib/autoload/sfSimpleAutoload.class.php
index 66ff5c1b4..8b44a7cbb 100755
--- a/lib/autoload/sfSimpleAutoload.class.php
+++ b/lib/autoload/sfSimpleAutoload.class.php
@@ -109,7 +109,7 @@ static public function unregister()
    */
   public function autoload($class)
   {
-    $class = strtolower($class);
+    $class = strtolower((string) $class);
 
     // class already exists
     if (class_exists($class, false) || interface_exists($class, false))
@@ -291,7 +291,7 @@ public function addFile($file, $register = true)
     preg_match_all('~^\s*(?:abstract\s+|final\s+)?(?:class|interface|trait)\s+(\w+)~mi', file_get_contents($file), $classes);
     foreach ($classes[1] as $class)
     {
-      $this->classes[strtolower($class)] = $file;
+      $this->classes[strtolower((string) $class)] = $file;
     }
   }
 
@@ -303,7 +303,7 @@ public function addFile($file, $register = true)
    */
   public function setClassPath($class, $path)
   {
-    $class = strtolower($class);
+    $class = strtolower((string) $class);
 
     $this->overriden[$class] = $path;
 
@@ -319,7 +319,7 @@ public function setClassPath($class, $path)
    */
   public function getClassPath($class)
   {
-    $class = strtolower($class);
+    $class = strtolower((string) $class);
 
     return isset($this->classes[$class]) ? $this->classes[$class] : null;
   }
diff --git a/lib/config/sfAutoloadConfigHandler.class.php b/lib/config/sfAutoloadConfigHandler.class.php
index 9132e5ce1..3b14b64f5 100755
--- a/lib/config/sfAutoloadConfigHandler.class.php
+++ b/lib/config/sfAutoloadConfigHandler.class.php
@@ -82,7 +82,7 @@ protected function parse(array $configFiles)
         // file mapping
         foreach ($entry['files'] as $class => $file)
         {
-          $mapping[strtolower($class)] = $file;
+          $mapping[strtolower((string) $class)] = $file;
         }
       }
       else
@@ -140,7 +140,7 @@ static public function parseFile($path, $file, $prefix)
         }
       }
 
-      $mapping[$localPrefix.strtolower($class)] = $file;
+      $mapping[$localPrefix.strtolower((string) $class)] = $file;
     }
 
     return $mapping;
diff --git a/lib/config/sfDefineEnvironmentConfigHandler.class.php b/lib/config/sfDefineEnvironmentConfigHandler.class.php
index 224dc2525..84ebeeac0 100644
--- a/lib/config/sfDefineEnvironmentConfigHandler.class.php
+++ b/lib/config/sfDefineEnvironmentConfigHandler.class.php
@@ -30,14 +30,14 @@ class sfDefineEnvironmentConfigHandler extends sfYamlConfigHandler
   public function execute($configFiles)
   {
     // get our prefix
-    $prefix = strtolower($this->getParameterHolder()->get('prefix', ''));
+    $prefix = strtolower((string) $this->getParameterHolder()->get('prefix', ''));
 
     // add module prefix if needed
     if ($this->getParameterHolder()->get('module', false))
     {
       $wildcardValues = $this->getParameterHolder()->get('wildcardValues');
       // either the module name is in wildcard values, or it needs to be inserted on runtime
-      $moduleName = $wildcardValues ? strtolower($wildcardValues[0]) : "'.strtolower(\$moduleName).'";
+      $moduleName = $wildcardValues ? strtolower((string) $wildcardValues[0]) : "'.strtolower(\$moduleName).'";
       $prefix .= $moduleName."_";
     }
 
@@ -82,7 +82,7 @@ protected function getValues($prefix, $category, $keys)
   {
     if (!is_array($keys))
     {
-      list($key, $value) = $this->fixCategoryValue($prefix.strtolower($category), '', $keys);
+      list($key, $value) = $this->fixCategoryValue($prefix.strtolower((string) $category), '', $keys);
 
       return array($key => $value);
     }
diff --git a/lib/controller/sfController.class.php b/lib/controller/sfController.class.php
index 6b69b857d..c2cef1684 100644
--- a/lib/controller/sfController.class.php
+++ b/lib/controller/sfController.class.php
@@ -108,8 +108,8 @@ protected function controllerExists($moduleName, $controllerName, $extension, $t
       $this->context->getConfigCache()->import('modules/'.$moduleName.'/config/generator.yml', false, true);
 
       // one action per file or one file for all actions
-      $classFile   = strtolower($extension);
-      $classSuffix = ucfirst(strtolower($extension));
+      $classFile   = strtolower((string) $extension);
+      $classSuffix = ucfirst(strtolower((string) $extension));
       $file        = $dir.'/'.$controllerName.$classSuffix.'.class.php';
       if (is_readable($file))
       {
@@ -208,15 +208,15 @@ public function forward($moduleName, $actionName)
     $this->getActionStack()->addEntry($moduleName, $actionName, $actionInstance);
 
     // include module configuration
-    $viewClass = sfConfig::get('mod_'.strtolower($moduleName).'_view_class', false);
+    $viewClass = sfConfig::get('mod_'.strtolower((string) $moduleName).'_view_class', false);
     require($this->context->getConfigCache()->checkConfig('modules/'.$moduleName.'/config/module.yml'));
     if (false !== $viewClass)
     {
-      sfConfig::set('mod_'.strtolower($moduleName).'_view_class', $viewClass);
+      sfConfig::set('mod_'.strtolower((string) $moduleName).'_view_class', $viewClass);
     }
 
     // module enabled?
-    if (sfConfig::get('mod_'.strtolower($moduleName).'_enabled'))
+    if (sfConfig::get('mod_'.strtolower((string) $moduleName).'_enabled'))
     {
       // check for a module config.php
       $moduleConfig = sfConfig::get('sf_app_module_dir').'/'.$moduleName.'/config/config.php';
@@ -296,7 +296,7 @@ public function getComponent($moduleName, $componentName)
    */
   protected function getController($moduleName, $controllerName, $extension)
   {
-    $classSuffix = ucfirst(strtolower($extension));
+    $classSuffix = ucfirst(strtolower((string) $extension));
     if (!isset($this->controllerClasses[$moduleName.'_'.$controllerName.'_'.$classSuffix]))
     {
       if (!$this->controllerExists($moduleName, $controllerName, $extension, true))
@@ -371,7 +371,7 @@ public function getView($moduleName, $actionName, $viewName)
     else
     {
       // view class (as configured in module.yml or defined in action)
-      $class = sfConfig::get('mod_'.strtolower($moduleName).'_view_class', 'sfPHP').'View';
+      $class = sfConfig::get('mod_'.strtolower((string) $moduleName).'_view_class', 'sfPHP').'View';
     }
 
     return new $class($this->context, $moduleName, $actionName, $viewName);
@@ -411,8 +411,8 @@ public function getPresentationFor($module, $action, $viewName = null)
     // set viewName if needed
     if ($viewName)
     {
-      $currentViewName = sfConfig::get('mod_'.strtolower($module).'_view_class');
-      sfConfig::set('mod_'.strtolower($module).'_view_class', $viewName);
+      $currentViewName = sfConfig::get('mod_'.strtolower((string) $module).'_view_class');
+      sfConfig::set('mod_'.strtolower((string) $module).'_view_class', $viewName);
     }
 
     try
@@ -428,7 +428,7 @@ public function getPresentationFor($module, $action, $viewName = null)
       // remove viewName
       if ($viewName)
       {
-        sfConfig::set('mod_'.strtolower($module).'_view_class', $currentViewName);
+        sfConfig::set('mod_'.strtolower((string) $module).'_view_class', $currentViewName);
       }
 
       throw $e;
@@ -462,7 +462,7 @@ public function getPresentationFor($module, $action, $viewName = null)
     // remove viewName
     if ($viewName)
     {
-      sfConfig::set('mod_'.strtolower($module).'_view_class', $currentViewName);
+      sfConfig::set('mod_'.strtolower((string) $module).'_view_class', $currentViewName);
     }
 
     return $presentation;
diff --git a/lib/debug/sfWebDebugPanelConfig.class.php b/lib/debug/sfWebDebugPanelConfig.class.php
index 5e212203b..8ff8645ed 100644
--- a/lib/debug/sfWebDebugPanelConfig.class.php
+++ b/lib/debug/sfWebDebugPanelConfig.class.php
@@ -71,7 +71,7 @@ public function getPanelContent()
    */
   protected function formatArrayAsHtml($id, $values)
   {
-    $id = ucfirst(strtolower($id));
+    $id = ucfirst(strtolower((string) $id));
 
     return '
     <h2>'.$id.' '.$this->getToggler('sfWebDebug'.$id).'</h2>
diff --git a/lib/form/sfForm.class.php b/lib/form/sfForm.class.php
index 2db45bbde..c23b133bf 100644
--- a/lib/form/sfForm.class.php
+++ b/lib/form/sfForm.class.php
@@ -1035,7 +1035,7 @@ public function isMultipart()
   public function renderFormTag($url, array $attributes = array())
   {
     $attributes['action'] = $url;
-    $attributes['method'] = isset($attributes['method']) ? strtolower($attributes['method']) : 'post';
+    $attributes['method'] = isset($attributes['method']) ? strtolower((string) $attributes['method']) : 'post';
     if ($this->isMultipart())
     {
       $attributes['enctype'] = 'multipart/form-data';
diff --git a/lib/helper/PartialHelper.php b/lib/helper/PartialHelper.php
index e20d0b9c2..78aa5ecb2 100644
--- a/lib/helper/PartialHelper.php
+++ b/lib/helper/PartialHelper.php
@@ -84,7 +84,7 @@ function has_component_slot($name)
   {
     return false;
   }
-  
+
   // check to see if component slot is empty (null)
   if ($viewInstance->getComponentSlot($name))
   {
@@ -138,7 +138,7 @@ function get_component($moduleName, $componentName, $vars = array())
 
   require($context->getConfigCache()->checkConfig('modules/'.$moduleName.'/config/module.yml'));
 
-  $class = sfConfig::get('mod_'.strtolower($moduleName).'_partial_view_class', 'sf').'PartialView';
+  $class = sfConfig::get('mod_'.strtolower((string) $moduleName).'_partial_view_class', 'sf').'PartialView';
   $view = new $class($context, $moduleName, $actionName, '');
   $view->setPartialVars(true === sfConfig::get('sf_escaping_strategy') ? sfOutputEscaper::unescape($vars) : $vars);
 
@@ -213,7 +213,7 @@ function get_partial($templateName, $vars = array())
   }
   $actionName = '_'.$templateName;
 
-  $class = sfConfig::get('mod_'.strtolower($moduleName).'_partial_view_class', 'sf').'PartialView';
+  $class = sfConfig::get('mod_'.strtolower((string) $moduleName).'_partial_view_class', 'sf').'PartialView';
   $view = new $class($context, $moduleName, $actionName, '');
   $view->setPartialVars(true === sfConfig::get('sf_escaping_strategy') ? sfOutputEscaper::unescape($vars) : $vars);
 
diff --git a/lib/helper/TextHelper.php b/lib/helper/TextHelper.php
index 5109b7798..ee6e2e57b 100644
--- a/lib/helper/TextHelper.php
+++ b/lib/helper/TextHelper.php
@@ -155,7 +155,7 @@ function excerpt_text($text, $phrase, $radius = 100, $excerpt_string = '...', $e
   $strtolower = ($mbstring) ? 'mb_strtolower' : 'strtolower';
   $substr = ($mbstring) ? 'mb_substr' : 'substr';
 
-  $found_pos = $strpos($strtolower($text), $strtolower($phrase));
+  $found_pos = $strpos($strtolower((string) $text), $strtolower((string) $phrase));
   $return_string = '';
   if ($found_pos !== false)
   {
diff --git a/lib/helper/UrlHelper.php b/lib/helper/UrlHelper.php
index de61246d2..1b11a9154 100644
--- a/lib/helper/UrlHelper.php
+++ b/lib/helper/UrlHelper.php
@@ -438,7 +438,7 @@ function form_tag($url_for_options = '', $options = array())
 
   $html_options = $options;
 
-  $html_options['method'] = isset($html_options['method']) ? strtolower($html_options['method']) : 'post';
+  $html_options['method'] = isset($html_options['method']) ? strtolower((string) $html_options['method']) : 'post';
 
   if (_get_option($html_options, 'multipart'))
   {
@@ -496,7 +496,7 @@ function mail_to($email, $name = '', $options = array(), $default_value = array(
   $default = array();
   foreach ($default_tmp as $key => $value)
   {
-    $default[] = urlencode($key).'='.urlencode($value);
+    $default[] = urlencode((string) $key).'='.urlencode((string) $value);
   }
   $options = count($default) ? '?'.implode('&', $default) : '';
 
@@ -605,10 +605,10 @@ function _method_javascript_function($method)
 {
   $function = "var f = document.createElement('form'); f.style.display = 'none'; this.parentNode.appendChild(f); f.method = 'post'; f.action = this.href;";
 
-  if ('post' != strtolower($method))
+  if ('post' != strtolower((string) $method))
   {
     $function .= "var m = document.createElement('input'); m.setAttribute('type', 'hidden'); ";
-    $function .= sprintf("m.setAttribute('name', 'sf_method'); m.setAttribute('value', '%s'); f.appendChild(m);", strtolower($method));
+    $function .= sprintf("m.setAttribute('name', 'sf_method'); m.setAttribute('value', '%s'); f.appendChild(m);", strtolower((string) $method));
   }
 
   // CSRF protection
diff --git a/lib/i18n/sfNumberFormat.class.php b/lib/i18n/sfNumberFormat.class.php
index bcf948d55..c84023349 100644
--- a/lib/i18n/sfNumberFormat.class.php
+++ b/lib/i18n/sfNumberFormat.class.php
@@ -116,7 +116,7 @@ function format($number, $pattern = 'd', $currency = 'USD', $charset = 'UTF-8')
   {
     $this->setPattern($pattern);
 
-    if (strtolower($pattern) == 'p')
+    if (strtolower((string) $pattern) == 'p')
     {
       $number *= 100;
     }
diff --git a/lib/mailer/sfMailer.class.php b/lib/mailer/sfMailer.class.php
index 86afba3e3..c688eb6e3 100755
--- a/lib/mailer/sfMailer.class.php
+++ b/lib/mailer/sfMailer.class.php
@@ -94,7 +94,7 @@ public function __construct(sfEventDispatcher $dispatcher, $options)
         {
           foreach ($transport->getExtensionHandlers() as $handler)
           {
-            if (in_array(strtolower($method), array_map('strtolower', (array) $handler->exposeMixinMethods())))
+            if (in_array(strtolower((string) $method), array_map('strtolower', (array) $handler->exposeMixinMethods())))
             {
               $transport->$method($value);
             }
diff --git a/lib/plugin/sfPearRestPlugin.class.php b/lib/plugin/sfPearRestPlugin.class.php
index 74b9dbabf..16f04a9f7 100644
--- a/lib/plugin/sfPearRestPlugin.class.php
+++ b/lib/plugin/sfPearRestPlugin.class.php
@@ -3,7 +3,7 @@
 /*
  * This file is part of the symfony package.
  * (c) Fabien Potencier <fabien.potencier@symfony-project.com>
- * 
+ *
  * For the full copyright and license information, please view the LICENSE
  * file that was distributed with this source code.
  */
@@ -86,7 +86,7 @@ public function getPluginLicense($plugin, $version)
 
     if (PEAR::isError($info))
     {
-      throw new sfPluginRestException(sprintf('Unable to get plugin licence information for plugin "%s": %s', $plugin, $info->getMessage())); 
+      throw new sfPluginRestException(sprintf('Unable to get plugin licence information for plugin "%s": %s', $plugin, $info->getMessage()));
     }
 
     if (null === $info)
@@ -113,7 +113,7 @@ public function getPluginLicense($plugin, $version)
    */
   public function getPluginVersions($plugin, $stability = null)
   {
-    $allreleases = $this->_rest->retrieveData($this->restBase.'r/'.strtolower($plugin).'/allreleases.xml');
+    $allreleases = $this->_rest->retrieveData($this->restBase.'r/'.strtolower((string) $plugin).'/allreleases.xml');
     if (PEAR::isError($allreleases))
     {
       throw new sfPluginRestException(sprintf('Unable to get information for plugin "%s": %s', $plugin, $allreleases->getMessage()));
@@ -159,7 +159,7 @@ public function getPluginVersions($plugin, $stability = null)
    */
   public function getPluginDependencies($plugin, $version)
   {
-    $dependencies = $this->_rest->retrieveData($this->restBase.'r/'.strtolower($plugin).'/deps.'.$version.'.txt');
+    $dependencies = $this->_rest->retrieveData($this->restBase.'r/'.strtolower((string) $plugin).'/deps.'.$version.'.txt');
     if (PEAR::isError($dependencies))
     {
       throw new sfPluginRestException(sprintf('Unable to get dependencies information for plugin "%s": %s', $plugin, $dependencies->getMessage()));
diff --git a/lib/plugins/sfDoctrinePlugin/data/generator/sfDoctrineModule/admin/parts/sortingAction.php b/lib/plugins/sfDoctrinePlugin/data/generator/sfDoctrineModule/admin/parts/sortingAction.php
index 937859a38..32e5c8158 100644
--- a/lib/plugins/sfDoctrinePlugin/data/generator/sfDoctrineModule/admin/parts/sortingAction.php
+++ b/lib/plugins/sfDoctrinePlugin/data/generator/sfDoctrineModule/admin/parts/sortingAction.php
@@ -5,7 +5,7 @@ protected function addSortQuery($query)
       return;
     }
 
-    if (!in_array(strtolower($sort[1]), array('asc', 'desc')))
+    if (!in_array(strtolower((string) $sort[1]), array('asc', 'desc')))
     {
       $sort[1] = 'asc';
     }
diff --git a/lib/plugins/sfDoctrinePlugin/data/generator/sfDoctrineModule/admin/template/templates/_filters.php b/lib/plugins/sfDoctrinePlugin/data/generator/sfDoctrineModule/admin/template/templates/_filters.php
index b8259edb3..7530bd7b6 100644
--- a/lib/plugins/sfDoctrinePlugin/data/generator/sfDoctrineModule/admin/template/templates/_filters.php
+++ b/lib/plugins/sfDoctrinePlugin/data/generator/sfDoctrineModule/admin/template/templates/_filters.php
@@ -27,7 +27,7 @@
             'help'       => $field->getConfig('help'),
             'form'       => $form,
             'field'      => $field,
-            'class'      => 'sf_admin_form_row sf_admin_'.strtolower($field->getType()).' sf_admin_filter_field_'.$name,
+            'class'      => 'sf_admin_form_row sf_admin_'.strtolower((string) $field->getType()).' sf_admin_filter_field_'.$name,
           )) ?]
         [?php endforeach; ?]
       </tbody>
diff --git a/lib/plugins/sfDoctrinePlugin/data/generator/sfDoctrineModule/admin/template/templates/_form_fieldset.php b/lib/plugins/sfDoctrinePlugin/data/generator/sfDoctrineModule/admin/template/templates/_form_fieldset.php
index ae30a30e6..093e47e1f 100644
--- a/lib/plugins/sfDoctrinePlugin/data/generator/sfDoctrineModule/admin/template/templates/_form_fieldset.php
+++ b/lib/plugins/sfDoctrinePlugin/data/generator/sfDoctrineModule/admin/template/templates/_form_fieldset.php
@@ -1,4 +1,4 @@
-<fieldset id="sf_fieldset_[?php echo preg_replace('/[^a-z0-9_]/', '_', strtolower($fieldset)) ?]">
+<fieldset id="sf_fieldset_[?php echo preg_replace('/[^a-z0-9_]/', '_', strtolower((string) $fieldset)) ?]">
   [?php if ('NONE' != $fieldset): ?]
     <h2>[?php echo __($fieldset, array(), '<?php echo $this->getI18nCatalogue() ?>') ?]</h2>
   [?php endif; ?]
@@ -12,7 +12,7 @@
       'help'       => $field->getConfig('help'),
       'form'       => $form,
       'field'      => $field,
-      'class'      => 'sf_admin_form_row sf_admin_'.strtolower($field->getType()).' sf_admin_form_field_'.$name,
+      'class'      => 'sf_admin_form_row sf_admin_'.strtolower((string) $field->getType()).' sf_admin_form_field_'.$name,
     )) ?]
   [?php endforeach; ?]
 </fieldset>
diff --git a/lib/plugins/sfDoctrinePlugin/data/generator/sfDoctrineModule/admin/template/templates/_list_td_tabular.php b/lib/plugins/sfDoctrinePlugin/data/generator/sfDoctrineModule/admin/template/templates/_list_td_tabular.php
index 4d56b50ef..97b003466 100644
--- a/lib/plugins/sfDoctrinePlugin/data/generator/sfDoctrineModule/admin/template/templates/_list_td_tabular.php
+++ b/lib/plugins/sfDoctrinePlugin/data/generator/sfDoctrineModule/admin/template/templates/_list_td_tabular.php
@@ -5,5 +5,5 @@
 </td>
 
 EOF
-, strtolower($field->getType()), $name, $this->renderField($field)), $field->getConfig()) ?>
+, strtolower((string) $field->getType()), $name, $this->renderField($field)), $field->getConfig()) ?>
 <?php endforeach; ?>
diff --git a/lib/plugins/sfDoctrinePlugin/data/generator/sfDoctrineModule/admin/template/templates/_list_th_tabular.php b/lib/plugins/sfDoctrinePlugin/data/generator/sfDoctrineModule/admin/template/templates/_list_th_tabular.php
index 298b900ee..7e8c13b4c 100644
--- a/lib/plugins/sfDoctrinePlugin/data/generator/sfDoctrineModule/admin/template/templates/_list_th_tabular.php
+++ b/lib/plugins/sfDoctrinePlugin/data/generator/sfDoctrineModule/admin/template/templates/_list_th_tabular.php
@@ -1,6 +1,6 @@
 <?php foreach ($this->configuration->getValue('list.display') as $name => $field): ?>
 [?php slot('sf_admin.current_header') ?]
-<th class="sf_admin_<?php echo strtolower($field->getType()) ?> sf_admin_list_th_<?php echo $name ?>">
+<th class="sf_admin_<?php echo strtolower((string) $field->getType()) ?> sf_admin_list_th_<?php echo $name ?>">
 <?php if ($field->isReal()): ?>
   [?php if ('<?php echo $name ?>' == $sort[0]): ?]
     [?php echo link_to(__('<?php echo $field->getConfig('label', '', true) ?>', array(), '<?php echo $this->getI18nCatalogue() ?>'), '@<?php echo $this->getUrlForAction('list') ?>', array('query_string' => 'sort=<?php echo $name ?>&sort_type='.($sort[1] == 'asc' ? 'desc' : 'asc'))) ?]
diff --git a/lib/plugins/sfDoctrinePlugin/lib/generator/sfDoctrineColumn.class.php b/lib/plugins/sfDoctrinePlugin/lib/generator/sfDoctrineColumn.class.php
index f693ebb55..a7ef82e15 100644
--- a/lib/plugins/sfDoctrinePlugin/lib/generator/sfDoctrineColumn.class.php
+++ b/lib/plugins/sfDoctrinePlugin/lib/generator/sfDoctrineColumn.class.php
@@ -203,7 +203,7 @@ public function getRelationKey($key)
     {
       $local = (array) $relation['local'];
       $local = array_map('strtolower', $local);
-      if (in_array(strtolower($this->name), $local))
+      if (in_array(strtolower((string) $this->name), $local))
       {
         return $relation[$key];
       }
@@ -268,7 +268,7 @@ public function isForeignKey()
     {
       $local = (array) $relation['local'];
       $local = array_map('strtolower', $local);
-      if (in_array(strtolower($this->name), $local))
+      if (in_array(strtolower((string) $this->name), $local))
       {
         $this->foreignClassName = $relation['class'];
         if ($relation->getType() === Doctrine_Relation::ONE)
diff --git a/lib/plugins/sfDoctrinePlugin/lib/record/sfDoctrineRecord.class.php b/lib/plugins/sfDoctrinePlugin/lib/record/sfDoctrineRecord.class.php
index c281b3358..9c0ea8086 100644
--- a/lib/plugins/sfDoctrinePlugin/lib/record/sfDoctrineRecord.class.php
+++ b/lib/plugins/sfDoctrinePlugin/lib/record/sfDoctrineRecord.class.php
@@ -152,7 +152,7 @@ public function __call($method, $arguments)
         }
         else if ($table->hasField($fieldName = $table->getFieldName($name)))
         {
-          $entityNameLower = strtolower($fieldName);
+          $entityNameLower = strtolower((string) $fieldName);
           if ($table->hasField($entityNameLower))
           {
             $entityName = $entityNameLower;
@@ -166,11 +166,11 @@ public function __call($method, $arguments)
           if ($table->hasField($underScored) || $table->hasRelation($underScored))
           {
             $entityName = $underScored;
-          } else if ($table->hasField(strtolower($name)) || $table->hasRelation(strtolower($name))) {
-            $entityName = strtolower($name);
+          } else if ($table->hasField(strtolower((string) $name)) || $table->hasRelation(strtolower((string) $name))) {
+            $entityName = strtolower((string) $name);
           } else {
             $camelCase = $table->getFieldName(sfInflector::camelize($name));
-            $camelCase = strtolower($camelCase[0]).substr($camelCase, 1, strlen($camelCase));
+            $camelCase = strtolower((string) $camelCase[0]).substr($camelCase, 1, strlen($camelCase));
             if ($table->hasField($camelCase) || $table->hasRelation($camelCase))
             {
               $entityName = $camelCase;
diff --git a/lib/plugins/sfDoctrinePlugin/lib/task/sfDoctrineCompileTask.class.php b/lib/plugins/sfDoctrinePlugin/lib/task/sfDoctrineCompileTask.class.php
index 11a9224e6..c2054d397 100644
--- a/lib/plugins/sfDoctrinePlugin/lib/task/sfDoctrineCompileTask.class.php
+++ b/lib/plugins/sfDoctrinePlugin/lib/task/sfDoctrineCompileTask.class.php
@@ -66,7 +66,7 @@ protected function execute($arguments = array(), $options = array())
     $drivers = array();
     foreach ($databaseManager->getNames() as $name)
     {
-      $drivers[] = strtolower($databaseManager->getDatabase($name)->getDoctrineConnection()->getDriverName());
+      $drivers[] = strtolower((string) $databaseManager->getDatabase($name)->getDoctrineConnection()->getDriverName());
     }
     $drivers = array_unique($drivers);
 
diff --git a/lib/request/sfWebRequest.class.php b/lib/request/sfWebRequest.class.php
index 99f8616e3..b46e2e5b9 100644
--- a/lib/request/sfWebRequest.class.php
+++ b/lib/request/sfWebRequest.class.php
@@ -507,7 +507,7 @@ public function getLanguages()
           {
             if ($i == 0)
             {
-              $lang = strtolower($codes[0]);
+              $lang = strtolower((string) $codes[0]);
             }
             else
             {
@@ -638,9 +638,9 @@ public function isSecure()
     $pathArray = $this->getPathInfoArray();
 
     return
-      (isset($pathArray['HTTPS']) && (('on' == strtolower($pathArray['HTTPS']) || 1 == $pathArray['HTTPS'])))
+      (isset($pathArray['HTTPS']) && (('on' == strtolower((string) $pathArray['HTTPS']) || 1 == $pathArray['HTTPS'])))
       ||
-      ($this->getOption('trust_proxy') && isset($pathArray['HTTP_SSL_HTTPS']) && (('on' == strtolower($pathArray['HTTP_SSL_HTTPS']) || 1 == $pathArray['HTTP_SSL_HTTPS'])))
+      ($this->getOption('trust_proxy') && isset($pathArray['HTTP_SSL_HTTPS']) && (('on' == strtolower((string) $pathArray['HTTP_SSL_HTTPS']) || 1 == $pathArray['HTTP_SSL_HTTPS'])))
       ||
       ($this->getOption('trust_proxy') && $this->isForwardedSecure())
     ;
@@ -655,7 +655,7 @@ protected function isForwardedSecure()
   {
     $pathArray = $this->getPathInfoArray();
 
-    return isset($pathArray['HTTP_X_FORWARDED_PROTO']) && 'https' == strtolower($pathArray['HTTP_X_FORWARDED_PROTO']);
+    return isset($pathArray['HTTP_X_FORWARDED_PROTO']) && 'https' == strtolower((string) $pathArray['HTTP_X_FORWARDED_PROTO']);
   }
 
   /**
diff --git a/lib/response/sfWebResponse.class.php b/lib/response/sfWebResponse.class.php
index 3bdc87639..786b67046 100644
--- a/lib/response/sfWebResponse.class.php
+++ b/lib/response/sfWebResponse.class.php
@@ -413,7 +413,7 @@ public function send()
    */
   protected function normalizeHeaderName($name)
   {
-    return strtr(ucwords(strtr(strtolower($name), array('_' => ' ', '-' => ' '))), array(' ' => '-'));
+    return strtr(ucwords(strtr(strtolower((string) $name), array('_' => ' ', '-' => ' '))), array(' ' => '-'));
   }
 
   /**
@@ -426,7 +426,7 @@ protected function normalizeHeaderName($name)
    */
   static public function getDate($timestamp, $type = 'rfc1123')
   {
-    $type = strtolower($type);
+    $type = strtolower((string) $type);
 
     if ($type == 'rfc1123')
     {
@@ -486,7 +486,7 @@ public function addCacheControlHttpHeader($name, $value = null)
         $currentHeaders[$tmp[0]] = isset($tmp[1]) ? $tmp[1] : null;
       }
     }
-    $currentHeaders[str_replace('_', '-', strtolower($name))] = $value;
+    $currentHeaders[str_replace('_', '-', strtolower((string) $name))] = $value;
 
     $headers = array();
     foreach ($currentHeaders as $key => $value)
@@ -561,7 +561,7 @@ public function getMetas()
    */
   public function addMeta($key, $value, $replace = true, $escape = true)
   {
-    $key = strtolower($key);
+    $key = strtolower((string) $key);
 
     if (null === $value)
     {
diff --git a/lib/routing/sfRequestRoute.class.php b/lib/routing/sfRequestRoute.class.php
index db3056fa5..4913500e0 100644
--- a/lib/routing/sfRequestRoute.class.php
+++ b/lib/routing/sfRequestRoute.class.php
@@ -57,7 +57,7 @@ public function matchesUrl($url, $context = array())
     }
 
     // enforce the sf_method requirement
-    if (in_array(strtolower($context['method']), $this->requirements['sf_method']))
+    if (in_array(strtolower((string) $context['method']), $this->requirements['sf_method']))
     {
       return $parameters;
     }
@@ -78,7 +78,7 @@ public function matchesParameters($params, $context = array())
     if (isset($params['sf_method']))
     {
       // enforce the sf_method requirement
-      if (!in_array(strtolower($params['sf_method']), $this->requirements['sf_method']))
+      if (!in_array(strtolower((string) $params['sf_method']), $this->requirements['sf_method']))
       {
         return false;
       }
diff --git a/lib/routing/sfRoute.class.php b/lib/routing/sfRoute.class.php
index f8a6ea7a5..d6c5c2b17 100644
--- a/lib/routing/sfRoute.class.php
+++ b/lib/routing/sfRoute.class.php
@@ -237,7 +237,7 @@ public function generate($params, $context = array(), $absolute = false)
       uasort($variables, array('sfRoute', 'generateCompareVarsByStrlen'));
       foreach ($variables as $variable => $value)
       {
-        $url = str_replace($value, urlencode($tparams[$variable]), $url);
+        $url = str_replace($value, urlencode((string) $tparams[$variable]), $url);
       }
 
       if(!in_array($this->suffix, $this->options['segment_separators']))
@@ -286,7 +286,7 @@ protected function generateWithTokens($parameters)
         case 'variable':
           if (!$optional || !isset($this->defaults[$token[3]]) || (isset($parameters[$token[3]]) && $parameters[$token[3]] != $this->defaults[$token[3]]))
           {
-            $url[] = urlencode($parameters[$token[3]]);
+            $url[] = urlencode((string) $parameters[$token[3]]);
             $optional = false;
           }
           break;
@@ -753,12 +753,12 @@ protected function generateStarParameter($url, $defaults, $parameters)
       {
         foreach ($value as $v)
         {
-          $tmp[] = $key.'='.urlencode($v);
+          $tmp[] = $key.'='.urlencode((string) $v);
         }
       }
       else
       {
-        $tmp[] = urlencode($key).'/'.urlencode($value);
+        $tmp[] = urlencode((string) $key).'/'.urlencode((string) $value);
       }
     }
     $tmp = implode('/', $tmp);
diff --git a/lib/service/sfServiceContainer.class.php b/lib/service/sfServiceContainer.class.php
index 35c5b70f6..d2fad8a01 100644
--- a/lib/service/sfServiceContainer.class.php
+++ b/lib/service/sfServiceContainer.class.php
@@ -70,7 +70,7 @@ public function setParameters(array $parameters)
     $this->parameters = array();
     foreach ($parameters as $key => $value)
     {
-      $this->parameters[strtolower($key)] = $value;
+      $this->parameters[strtolower((string) $key)] = $value;
     }
   }
 
@@ -107,7 +107,7 @@ public function getParameter($name)
   {
     if ($this->hasParameter($name))
     {
-      return $this->parameters[strtolower($name)];
+      return $this->parameters[strtolower((string) $name)];
     }
 
     if (sfConfig::has($name))
@@ -126,7 +126,7 @@ public function getParameter($name)
    */
   public function setParameter($name, $value)
   {
-    $this->parameters[strtolower($name)] = $value;
+    $this->parameters[strtolower((string) $name)] = $value;
   }
 
   /**
@@ -138,7 +138,7 @@ public function setParameter($name, $value)
    */
   public function hasParameter($name)
   {
-    return array_key_exists(strtolower($name), $this->parameters);
+    return array_key_exists(strtolower((string) $name), $this->parameters);
   }
 
   /**
diff --git a/lib/service/sfServiceContainerDumperPhp.class.php b/lib/service/sfServiceContainerDumperPhp.class.php
index 88095c7ce..b13b1e4fc 100644
--- a/lib/service/sfServiceContainerDumperPhp.class.php
+++ b/lib/service/sfServiceContainerDumperPhp.class.php
@@ -339,7 +339,7 @@ protected function dumpValue($value)
     }
     elseif (is_object($value) && $value instanceof sfServiceParameter)
     {
-      return sprintf("\$this->getParameter('%s')", strtolower($value));
+      return sprintf("\$this->getParameter('%s')", strtolower((string) $value));
     }
     elseif (is_string($value))
     {
@@ -347,7 +347,7 @@ protected function dumpValue($value)
       {
         // we do this to deal with non string values (boolean, integer, ...)
         // the preg_replace_callback converts them to strings
-        return sprintf("\$this->getParameter('%s')", strtolower($match[1]));
+        return sprintf("\$this->getParameter('%s')", strtolower((string) $match[1]));
       }
       else
       {
@@ -371,7 +371,7 @@ protected function dumpValue($value)
 
   public function replaceParameter($match)
   {
-    return sprintf("'.\$this->getParameter('%s').'", strtolower($match[2]));
+    return sprintf("'.\$this->getParameter('%s').'", strtolower((string) $match[2]));
   }
 
   protected function getServiceCall($id)
diff --git a/lib/service/sfServiceContainerLoaderArray.class.php b/lib/service/sfServiceContainerLoaderArray.class.php
index b5c214291..436464944 100644
--- a/lib/service/sfServiceContainerLoaderArray.class.php
+++ b/lib/service/sfServiceContainerLoaderArray.class.php
@@ -31,7 +31,7 @@ public function doLoad($content)
     {
       foreach ($content['parameters'] as $key => $value)
       {
-        $parameters[strtolower($key)] = $this->resolveServices($value);
+        $parameters[strtolower((string) $key)] = $this->resolveServices($value);
       }
     }
 
diff --git a/lib/task/generator/sfGenerateProjectTask.class.php b/lib/task/generator/sfGenerateProjectTask.class.php
index 1cfcb4343..c2099956b 100755
--- a/lib/task/generator/sfGenerateProjectTask.class.php
+++ b/lib/task/generator/sfGenerateProjectTask.class.php
@@ -87,7 +87,7 @@ protected function execute($arguments = array(), $options = array())
       throw new sfCommandException(sprintf('A symfony project already exists in this directory (%s).', getcwd()));
     }
 
-    if (!in_array(strtolower($options['orm']), array('doctrine', 'none')))
+    if (!in_array(strtolower((string) $options['orm']), array('doctrine', 'none')))
     {
       throw new InvalidArgumentException(sprintf('Invalid ORM name "%s".', $options['orm']));
     }
@@ -98,7 +98,7 @@ protected function execute($arguments = array(), $options = array())
     }
 
     // clean orm option
-    $options['orm'] = ucfirst(strtolower($options['orm']));
+    $options['orm'] = ucfirst(strtolower((string) $options['orm']));
 
     $this->arguments = $arguments;
     $this->options = $options;
diff --git a/lib/task/plugin/sfPluginInstallTask.class.php b/lib/task/plugin/sfPluginInstallTask.class.php
index a6b1fe1f6..5434f80b2 100644
--- a/lib/task/plugin/sfPluginInstallTask.class.php
+++ b/lib/task/plugin/sfPluginInstallTask.class.php
@@ -3,7 +3,7 @@
 /*
  * This file is part of the symfony package.
  * (c) 2004-2006 Fabien Potencier <fabien.potencier@symfony-project.com>
- * 
+ *
  * For the full copyright and license information, please view the LICENSE
  * file that was distributed with this source code.
  */
@@ -111,7 +111,7 @@ protected function execute($arguments = array(), $options = array())
 
       if (false !== $license)
       {
-        $temp = trim(str_replace('license', '', strtolower($license)));
+        $temp = trim(str_replace('license', '', strtolower((string) $license)));
         if (null !== $license && !in_array($temp, array('mit', 'bsd', 'lgpl', 'php', 'apache')))
         {
           throw new sfCommandException(sprintf('The license of this plugin "%s" is not MIT like (use --force-license to force installation).', $license));
diff --git a/lib/task/sfTask.class.php b/lib/task/sfTask.class.php
index 0a4e69072..5f52d84fd 100644
--- a/lib/task/sfTask.class.php
+++ b/lib/task/sfTask.class.php
@@ -496,18 +496,18 @@ public function ask($question, $style = 'QUESTION', $default = null)
   public function askConfirmation($question, $style = 'QUESTION', $default = true)
   {
     $answer = 'z';
-    while ($answer && !in_array(strtolower($answer[0]), array('y', 'n')))
+    while ($answer && !in_array(strtolower((string) $answer[0]), array('y', 'n')))
     {
       $answer = $this->ask($question, $style);
     }
 
     if (false === $default)
     {
-      return $answer && 'y' == strtolower($answer[0]);
+      return $answer && 'y' == strtolower((string) $answer[0]);
     }
     else
     {
-      return !$answer || 'y' == strtolower($answer[0]);
+      return !$answer || 'y' == strtolower((string) $answer[0]);
     }
   }
 
diff --git a/lib/test/sfTestFunctionalBase.class.php b/lib/test/sfTestFunctionalBase.class.php
index fc83df3b5..a32569fc8 100644
--- a/lib/test/sfTestFunctionalBase.class.php
+++ b/lib/test/sfTestFunctionalBase.class.php
@@ -236,7 +236,7 @@ public function call($uri, $method = 'get', $parameters = array(), $changeStack
 
     $uri = $this->browser->fixUri($uri);
 
-    $this->test()->comment(sprintf('%s %s', strtolower($method), $uri));
+    $this->test()->comment(sprintf('%s %s', strtolower((string) $method), $uri));
 
     foreach ($this->testers as $tester)
     {
diff --git a/lib/util/sfDomCssSelector.class.php b/lib/util/sfDomCssSelector.class.php
index a207f4e75..df094eac8 100644
--- a/lib/util/sfDomCssSelector.class.php
+++ b/lib/util/sfDomCssSelector.class.php
@@ -118,7 +118,7 @@ protected function getElementsForNode($selector, $root_node)
           $id = substr($token, $pos + 1);
           $xpath = new DomXPath($root_node);
           $element = $xpath->query(sprintf("//*[@id = '%s']", $id))->item(0);
-          if (!$element || ($tagName && strtolower($element->nodeName) != $tagName))
+          if (!$element || ($tagName && strtolower((string) $element->nodeName) != $tagName))
           {
             // tag with that ID not found
             return array();
diff --git a/lib/util/sfFinder.class.php b/lib/util/sfFinder.class.php
index be56137a3..fab6c73fd 100644
--- a/lib/util/sfFinder.class.php
+++ b/lib/util/sfFinder.class.php
@@ -97,7 +97,7 @@ public static function type($name)
    */
   public function setType($name)
   {
-    $name = strtolower($name);
+    $name = strtolower((string) $name);
 
     if (substr($name, 0, 3) === 'dir')
     {
@@ -759,12 +759,12 @@ public function test($number)
 
     $target = array_key_exists(2, $matches) ? $matches[2] : '';
     $magnitude = array_key_exists(3, $matches) ? $matches[3] : '';
-    if (strtolower($magnitude) === 'k')  $target *=           1000;
-    if (strtolower($magnitude) === 'ki') $target *=           1024;
-    if (strtolower($magnitude) === 'm')  $target *=        1000000;
-    if (strtolower($magnitude) === 'mi') $target *=      1024*1024;
-    if (strtolower($magnitude) === 'g')  $target *=     1000000000;
-    if (strtolower($magnitude) === 'gi') $target *= 1024*1024*1024;
+    if (strtolower((string) $magnitude) === 'k')  $target *=           1000;
+    if (strtolower((string) $magnitude) === 'ki') $target *=           1024;
+    if (strtolower((string) $magnitude) === 'm')  $target *=        1000000;
+    if (strtolower((string) $magnitude) === 'mi') $target *=      1024*1024;
+    if (strtolower((string) $magnitude) === 'g')  $target *=     1000000000;
+    if (strtolower((string) $magnitude) === 'gi') $target *= 1024*1024*1024;
 
     $comparison = array_key_exists(1, $matches) ? $matches[1] : '==';
     if ($comparison === '==' || $comparison == '')
diff --git a/lib/util/sfInflector.class.php b/lib/util/sfInflector.class.php
index f1676eb06..507bf6e80 100644
--- a/lib/util/sfInflector.class.php
+++ b/lib/util/sfInflector.class.php
@@ -45,7 +45,7 @@ public static function underscore($camel_cased_word)
     $tmp = sfToolkit::pregtr($tmp, array('/([A-Z]+)([A-Z][a-z])/' => '\\1_\\2',
                                          '/([a-z\d])([A-Z])/'     => '\\1_\\2'));
 
-    return strtolower($tmp);
+    return strtolower((string) $tmp);
   }
 
   /**
diff --git a/lib/util/sfToolkit.class.php b/lib/util/sfToolkit.class.php
index 811df0edb..38081a809 100644
--- a/lib/util/sfToolkit.class.php
+++ b/lib/util/sfToolkit.class.php
@@ -305,7 +305,7 @@ public static function literalize($value, $quoted = false)
   {
     // lowercase our value for comparison
     $value  = trim($value);
-    $lvalue = strtolower($value);
+    $lvalue = strtolower((string) $value);
 
     if (in_array($lvalue, array('null', '~', '')))
     {
@@ -354,7 +354,7 @@ public static function replaceConstants($value)
     }
 
     return preg_replace_callback('/%(.+?)%/', function ($v) {
-      return sfConfig::has(strtolower($v[1])) ? sfConfig::get(strtolower($v[1])) : '%'.$v[1].'%';
+      return sfConfig::has(strtolower((string) $v[1])) ? sfConfig::get(strtolower((string) $v[1])) : '%'.$v[1].'%';
     }, $value);
   }
 
diff --git a/lib/validator/sfValidatorFile.class.php b/lib/validator/sfValidatorFile.class.php
index 294dea8c0..7fad1006b 100644
--- a/lib/validator/sfValidatorFile.class.php
+++ b/lib/validator/sfValidatorFile.class.php
@@ -132,7 +132,7 @@ protected function doClean($value)
           $max = min($max, $this->getOption('max_size'));
         }
         throw new sfValidatorError($this, 'max_size', array(
-          'max_size' => round($max / 1024, 0), 
+          'max_size' => round($max / 1024, 0),
           'size' => (int) $value['size']
         ));
       case UPLOAD_ERR_FORM_SIZE:
@@ -154,7 +154,7 @@ protected function doClean($value)
     if ($this->hasOption('max_size') && $this->getOption('max_size') < (int) $value['size'])
     {
       throw new sfValidatorError($this, 'max_size', array(
-        'max_size' => round($this->getOption('max_size') / 1024, 0), 
+        'max_size' => round($this->getOption('max_size') / 1024, 0),
         'size' => (int) $value['size']
       ));
     }
@@ -198,11 +198,11 @@ protected function getMimeType($file, $fallback)
 
       if (null !== $type && $type !== false)
       {
-        return strtolower($type);
+        return strtolower((string) $type);
       }
     }
 
-    return strtolower($fallback);
+    return strtolower((string) $fallback);
   }
 
   /**
diff --git a/lib/validator/sfValidatorFromDescription.class.php b/lib/validator/sfValidatorFromDescription.class.php
index 16bd206fd..c870821fc 100644
--- a/lib/validator/sfValidatorFromDescription.class.php
+++ b/lib/validator/sfValidatorFromDescription.class.php
@@ -104,7 +104,7 @@ protected function tokenize($string)
         // arguments (optional)
         $arguments = $this->parseArguments($string, $i);
 
-        $tokens[] = new sfValidatorFDTokenOperator(strtolower($match[1]), $arguments);
+        $tokens[] = new sfValidatorFDTokenOperator(strtolower((string) $match[1]), $arguments);
       }
       else if (preg_match('/^(?:([a-z0-9_\-]+)\:)?([a-z0-9_\-]+)/i', substr($string, $i), $match))
       {
diff --git a/lib/validator/sfValidatorSchema.class.php b/lib/validator/sfValidatorSchema.class.php
index 34c97180e..7ff321f52 100644
--- a/lib/validator/sfValidatorSchema.class.php
+++ b/lib/validator/sfValidatorSchema.class.php
@@ -396,7 +396,7 @@ protected function getBytes($value)
   {
     $value    = trim($value);
     $number   = (float) $value;
-    $modifier = strtolower($value[strlen($value) - 1]);
+    $modifier = strtolower((string) $value[strlen($value) - 1]);
 
     $exp_by_modifier = array(
       'k' => 1,
diff --git a/lib/view/sfView.class.php b/lib/view/sfView.class.php
index 87107d59c..b72d2fca5 100644
--- a/lib/view/sfView.class.php
+++ b/lib/view/sfView.class.php
@@ -117,7 +117,7 @@ public function initialize($context, $moduleName, $actionName, $viewName)
     $this->attributeHolder = $this->initializeAttributeHolder();
 
     $this->parameterHolder = new sfParameterHolder();
-    $this->parameterHolder->add(sfConfig::get('mod_'.strtolower($moduleName).'_view_param', array()));
+    $this->parameterHolder->add(sfConfig::get('mod_'.strtolower((string) $moduleName).'_view_param', array()));
 
     $request = $context->getRequest();
 
diff --git a/lib/view/sfViewCacheManager.class.php b/lib/view/sfViewCacheManager.class.php
index 70198e10f..332c875b2 100644
--- a/lib/view/sfViewCacheManager.class.php
+++ b/lib/view/sfViewCacheManager.class.php
@@ -263,7 +263,7 @@ protected function getCacheKeyHostNamePart($hostName = '')
     $hostName = preg_replace('/[^a-z0-9\*]/i', '_', $hostName);
     $hostName = preg_replace('/_+/', '_', $hostName);
 
-    return strtolower($hostName);
+    return strtolower((string) $hostName);
   }
 
   /**
@@ -307,7 +307,7 @@ public function addCache($moduleName, $actionName, $options = array())
     {
       foreach ($options['vary'] as $key => $name)
       {
-        $options['vary'][$key] = str_replace('_', '-', strtolower($name));
+        $options['vary'][$key] = str_replace('_', '-', strtolower((string) $name));
       }
     }
 
diff --git a/lib/widget/sfWidget.class.php b/lib/widget/sfWidget.class.php
index 80a4c4b63..58e45c327 100644
--- a/lib/widget/sfWidget.class.php
+++ b/lib/widget/sfWidget.class.php
@@ -332,7 +332,7 @@ public function renderTag($tag, $attributes = array())
       return '';
     }
 
-    return sprintf('<%s%s%s', $tag, $this->attributesToHtml($attributes), self::$xhtml ? ' />' : (strtolower($tag) == 'input' ? '>' : sprintf('></%s>', $tag)));
+    return sprintf('<%s%s%s', $tag, $this->attributesToHtml($attributes), self::$xhtml ? ' />' : (strtolower((string) $tag) == 'input' ? '>' : sprintf('></%s>', $tag)));
   }
 
   /**
diff --git a/lib/yaml/sfYamlInline.class.php b/lib/yaml/sfYamlInline.class.php
index 97d8c5b03..2b96ef231 100644
--- a/lib/yaml/sfYamlInline.class.php
+++ b/lib/yaml/sfYamlInline.class.php
@@ -109,11 +109,11 @@ static public function dump($value)
         return "''";
       case preg_match(self::getTimestampRegex(), $value):
         return "'$value'";
-      case in_array(strtolower($value), $trueValues):
+      case in_array(strtolower((string) $value), $trueValues):
         return "'$value'";
-      case in_array(strtolower($value), $falseValues):
+      case in_array(strtolower((string) $value), $falseValues):
         return "'$value'";
-      case in_array(strtolower($value), array('null', '~')):
+      case in_array(strtolower((string) $value), array('null', '~')):
         return "'$value'";
       default:
         return $value;
@@ -387,7 +387,7 @@ static protected function evaluateScalar($scalar)
 
     switch (true)
     {
-      case 'null' == strtolower($scalar):
+      case 'null' == strtolower((string) $scalar):
       case '' == $scalar:
       case '~' == $scalar:
         return null;
@@ -401,9 +401,9 @@ static protected function evaluateScalar($scalar)
         $raw = $scalar;
         $cast = (int) $scalar;
         return '0' == $scalar[0] ? octdec($scalar) : (((string) $raw == (string) $cast) ? $cast : $raw);
-      case in_array(strtolower($scalar), $trueValues):
+      case in_array(strtolower((string) $scalar), $trueValues):
         return true;
-      case in_array(strtolower($scalar), $falseValues):
+      case in_array(strtolower((string) $scalar), $falseValues):
         return false;
       case 0 === strpos($scalar, '0x'):
         return hexdec($scalar);
diff --git a/test/unit/routing/sfRouteTest.php b/test/unit/routing/sfRouteTest.php
index ff50cee0b..1d42d45f4 100644
--- a/test/unit/routing/sfRouteTest.php
+++ b/test/unit/routing/sfRouteTest.php
@@ -3,7 +3,7 @@
 /*
  * This file is part of the symfony package.
  * (c) Fabien Potencier <fabien.potencier@symfony-project.com>
- * 
+ *
  * For the full copyright and license information, please view the LICENSE
  * file that was distributed with this source code.
  */
@@ -227,7 +227,7 @@ protected function generateForLabel($optional, $tparams, $separator, $name, $var
   {
     if (!empty($tparams[$variable]) && (!$optional || !isset($this->defaults[$variable]) || $tparams[$variable] != $this->defaults[$variable]))
     {
-      return $variable . '/' . urlencode($tparams[$variable]);
+      return $variable . '/' . urlencode((string) $tparams[$variable]);
     }
   }
 }