Added Request::beforeSend callback.

src/Httpful/Request.php

@@ -44,6 +44,7 @@ class Request
            $payload,
            $parse_callback,
            $error_callback,
+           $send_callback,
            $follow_redirects        = false,
            $max_redirects           = self::MAX_REDIRECTS_DEFAULT,
            $payload_serializers     = array();
@@ -648,6 +649,18 @@ public function whenError(\Closure $callback)
         return $this;
     }
 
+    /**
+     * Callback invoked after payload has been serialized but before
+     * the request has been built.
+     * @return Request this
+     * @param \Closure $callback (Request $request)
+     */
+    public function beforeSend(\Closure $callback)
+    {
+        $this->send_callback = $callback;
+        return $this;
+    }
+
     /**
      * Register a callback that will be used to serialize the payload
      * for a particular mime type.  When using "*" for the mime
@@ -825,6 +838,14 @@ public function _curlPrep()
         if (!isset($this->uri))
             throw new \Exception('Attempting to send a request before defining a URI endpoint.');
 
+        if (isset($this->payload)) {
+            $this->serialized_payload = $this->_serializePayload($this->payload);
+        }
+
+        if (isset($this->send_callback)) {
+            call_user_func($this->send_callback, $this);
+        }
+
         $ch = curl_init($this->uri);
 
         curl_setopt($ch, CURLOPT_CUSTOMREQUEST, $this->method);
@@ -876,7 +897,6 @@ public function _curlPrep()
         // https://github.com/nategood/httpful/issues/84
         // set Content-Length to the size of the payload if present
         if (isset($this->payload)) {
-            $this->serialized_payload = $this->_serializePayload($this->payload);
             curl_setopt($ch, CURLOPT_POSTFIELDS, $this->serialized_payload);
             if (!$this->isUpload()) {
                 $this->headers['Content-Length'] =

tests/Httpful/HttpfulTest.php

@@ -411,6 +411,31 @@ function testWhenError() {
         $this->assertTrue($caught);
     }
 
+    function testBeforeSend() {
+        $invoked = false;
+        $changed = false;
+        $self = $this;
+
+        try {
+            Request::get('malformed://url')
+                ->beforeSend(function($request) use(&$invoked,$self) {
+                    $self->assertEquals('malformed://url', $request->uri);
+                    $self->assertEquals('A payload', $request->serialized_payload);
+                    $request->uri('malformed2://url');
+                    $invoked = true;
+                })
+                ->whenError(function($error) { /* Be silent */ })
+                ->body('A payload')
+                ->send();
+        } catch (\Httpful\Exception\ConnectionErrorException $e) {
+            $this->assertTrue(strpos($e->getMessage(), 'malformed2') !== false);
+            $changed = true;
+        }
+
+        $this->assertTrue($invoked);
+        $this->assertTrue($changed);
+    }
+
     function test_parseCode()
     {
         $req = Request::init()->sendsAndExpects(Mime::JSON);