diff --git a/modules/openapi-generator/src/main/resources/php-nextgen/ObjectSerializer.mustache b/modules/openapi-generator/src/main/resources/php-nextgen/ObjectSerializer.mustache
index 5efe3ede3a50..5f8627566409 100644
--- a/modules/openapi-generator/src/main/resources/php-nextgen/ObjectSerializer.mustache
+++ b/modules/openapi-generator/src/main/resources/php-nextgen/ObjectSerializer.mustache
@@ -19,6 +19,7 @@
 
 namespace {{invokerPackage}};
 
+use BackedEnum;
 use DateTimeInterface;
 use DateTime;
 use GuzzleHttp\Psr7\Utils;
@@ -254,6 +255,11 @@ class ObjectSerializer
                         // push key itself
                         $result[] = $prop;
                     }
+
+                    if ($v instanceof BackedEnum) {
+                        $v = $v->value;
+                    }
+
                     $result[$prop] = $v;
                 }
             }
diff --git a/samples/client/echo_api/php-nextgen-streaming/src/ObjectSerializer.php b/samples/client/echo_api/php-nextgen-streaming/src/ObjectSerializer.php
index 90819e57ca01..534813b526f5 100644
--- a/samples/client/echo_api/php-nextgen-streaming/src/ObjectSerializer.php
+++ b/samples/client/echo_api/php-nextgen-streaming/src/ObjectSerializer.php
@@ -28,6 +28,7 @@
 
 namespace OpenAPI\Client;
 
+use BackedEnum;
 use DateTimeInterface;
 use DateTime;
 use GuzzleHttp\Psr7\Utils;
@@ -263,6 +264,11 @@ public static function toQueryValue(
                         // push key itself
                         $result[] = $prop;
                     }
+
+                    if ($v instanceof BackedEnum) {
+                        $v = $v->value;
+                    }
+
                     $result[$prop] = $v;
                 }
             }
diff --git a/samples/client/echo_api/php-nextgen/src/ObjectSerializer.php b/samples/client/echo_api/php-nextgen/src/ObjectSerializer.php
index 90819e57ca01..534813b526f5 100644
--- a/samples/client/echo_api/php-nextgen/src/ObjectSerializer.php
+++ b/samples/client/echo_api/php-nextgen/src/ObjectSerializer.php
@@ -28,6 +28,7 @@
 
 namespace OpenAPI\Client;
 
+use BackedEnum;
 use DateTimeInterface;
 use DateTime;
 use GuzzleHttp\Psr7\Utils;
@@ -263,6 +264,11 @@ public static function toQueryValue(
                         // push key itself
                         $result[] = $prop;
                     }
+
+                    if ($v instanceof BackedEnum) {
+                        $v = $v->value;
+                    }
+
                     $result[$prop] = $v;
                 }
             }
diff --git a/samples/client/petstore/php-nextgen/OpenAPIClient-php/src/ObjectSerializer.php b/samples/client/petstore/php-nextgen/OpenAPIClient-php/src/ObjectSerializer.php
index 7ba4d1552fcb..00cca1a05a78 100644
--- a/samples/client/petstore/php-nextgen/OpenAPIClient-php/src/ObjectSerializer.php
+++ b/samples/client/petstore/php-nextgen/OpenAPIClient-php/src/ObjectSerializer.php
@@ -27,6 +27,7 @@
 
 namespace OpenAPI\Client;
 
+use BackedEnum;
 use DateTimeInterface;
 use DateTime;
 use GuzzleHttp\Psr7\Utils;
@@ -262,6 +263,11 @@ public static function toQueryValue(
                         // push key itself
                         $result[] = $prop;
                     }
+
+                    if ($v instanceof BackedEnum) {
+                        $v = $v->value;
+                    }
+
                     $result[$prop] = $v;
                 }
             }