diff --git a/src/main/java/io/swagger/codegen/v3/generators/php/PhpClientCodegen.java b/src/main/java/io/swagger/codegen/v3/generators/php/PhpClientCodegen.java
index 8023500f92..daec128c11 100644
--- a/src/main/java/io/swagger/codegen/v3/generators/php/PhpClientCodegen.java
+++ b/src/main/java/io/swagger/codegen/v3/generators/php/PhpClientCodegen.java
@@ -110,7 +110,7 @@ public PhpClientCodegen() {
 
         instantiationTypes.put("array", "array");
         instantiationTypes.put("map", "map");
-        
+
         // provide primitives to mustache template
         List<String> sortedLanguageSpecificPrimitives= new ArrayList<String>(languageSpecificPrimitives);
         Collections.sort(sortedLanguageSpecificPrimitives);
@@ -295,6 +295,12 @@ public void processOpts() {
         if (additionalProperties.containsKey(VARIABLE_NAMING_CONVENTION)) {
             this.setParameterNamingConvention((String) additionalProperties.get(VARIABLE_NAMING_CONVENTION));
         }
+        if (StringUtils.isBlank(composerVendorName) && additionalProperties.get(CodegenConstants.GIT_USER_ID) != null) {
+            additionalProperties.put(CodegenConstants.GIT_USER_ID, StringUtils.lowerCase(additionalProperties.get(CodegenConstants.GIT_USER_ID).toString()));
+        }
+        if (StringUtils.isBlank(composerProjectName) && additionalProperties.get(CodegenConstants.GIT_REPO_ID) != null) {
+            additionalProperties.put(CodegenConstants.GIT_REPO_ID, StringUtils.lowerCase(additionalProperties.get(CodegenConstants.GIT_REPO_ID).toString()));
+        }
 
         additionalProperties.put("escapedInvokerPackage", invokerPackage.replace("\\", "\\\\"));
 
diff --git a/src/main/resources/handlebars/php/.php_cs b/src/main/resources/handlebars/php/.php_cs
index 6b8e23c818..4fbe53ec5f 100644
--- a/src/main/resources/handlebars/php/.php_cs
+++ b/src/main/resources/handlebars/php/.php_cs
@@ -1,18 +1,23 @@
 <?php
 
-return Symfony\CS\Config::create()
-    ->level(Symfony\CS\FixerInterface::PSR2_LEVEL)
+return PhpCsFixer\Config::create()
     ->setUsingCache(true)
-    ->fixers(
-        [
-            'ordered_use',
-            'phpdoc_order',
-            'short_array_syntax',
-            'strict',
-            'strict_param'
-        ]
-    )
-    ->finder(
-        Symfony\CS\Finder\DefaultFinder::create()
-            ->in(__DIR__)
+    ->setRules([
+        '@PSR2' => true,
+        'ordered_imports' => true,
+        'phpdoc_order' => true,
+        'array_syntax' => [ 'syntax' => 'short' ],
+        'strict_comparison' => true,
+        'strict_param' => true,
+        'no_trailing_whitespace' => false,
+        'no_trailing_whitespace_in_comment' => false,
+        'braces' => false,
+        'single_blank_line_at_eof' => false,
+        'blank_line_after_namespace' => false,
+    ])
+    ->setFinder(
+        PhpCsFixer\Finder::create()
+        ->exclude('test')
+        ->exclude('tests')
+        ->in(__DIR__)
     );
diff --git a/src/main/resources/handlebars/php/HeaderSelector.mustache b/src/main/resources/handlebars/php/HeaderSelector.mustache
index 909beb134d..72f585b46c 100644
--- a/src/main/resources/handlebars/php/HeaderSelector.mustache
+++ b/src/main/resources/handlebars/php/HeaderSelector.mustache
@@ -97,4 +97,3 @@ class HeaderSelector
         }
     }
 }
-
diff --git a/src/main/resources/handlebars/php/ObjectSerializer.mustache b/src/main/resources/handlebars/php/ObjectSerializer.mustache
index 7dac80ddae..dff5417ab1 100644
--- a/src/main/resources/handlebars/php/ObjectSerializer.mustache
+++ b/src/main/resources/handlebars/php/ObjectSerializer.mustache
@@ -33,11 +33,12 @@ class ObjectSerializer
      * Serialize data
      *
      * @param mixed  $data   the data to serialize
+     * @param string $type   the SwaggerType of the data
      * @param string $format the format of the Swagger type of the data
      *
      * @return string|object serialized form of $data
      */
-    public static function sanitizeForSerialization($data, $format = null)
+    public static function sanitizeForSerialization($data, $type = null, $format = null)
     {
         if (is_scalar($data) || null === $data) {
             return $data;
@@ -48,6 +49,11 @@ class ObjectSerializer
                 $data[$property] = self::sanitizeForSerialization($value);
             }
             return $data;
+        } elseif ($data instanceof \stdClass) {
+            foreach ($data as $property => $value) {
+                $data->$property = self::sanitizeForSerialization($value);
+            }
+            return $data;
         } elseif (is_object($data)) {
             $values = [];
             $formats = $data::swaggerFormats();
@@ -57,7 +63,7 @@ class ObjectSerializer
                 if ($value !== null
                     && !in_array($swaggerType, [{{&primitives}}], true)
                     && method_exists($swaggerType, 'getAllowableEnumValues')
-                    && !in_array($value, $swaggerType::getAllowableEnumValues())) {
+                    && !in_array($value, $swaggerType::getAllowableEnumValues(), true)) {
                     $imploded = implode("', '", $swaggerType::getAllowableEnumValues());
                     throw new \InvalidArgumentException("Invalid value for enum '$swaggerType', must be one of: '$imploded'");
                 }
@@ -108,23 +114,22 @@ class ObjectSerializer
      * later.
      *
      * @param string[]|string|\DateTime $object an object to be serialized to a string
-     * @param string|null $format the format of the parameter
      *
      * @return string the serialized object
      */
-    public static function toQueryValue($object, $format = null)
+    public static function toQueryValue($object)
     {
         if (is_array($object)) {
             return implode(',', $object);
         } else {
-            return self::toString($object, $format);
+            return self::toString($object);
         }
     }
 
     /**
      * Take value and turn it into a string suitable for inclusion in
      * the header. If it's a string, pass through unchanged
-     * If it's a datetime object, format it in RFC3339
+     * If it's a datetime object, format it in ISO8601
      *
      * @param string $value a string which will be part of the header
      *
@@ -138,7 +143,7 @@ class ObjectSerializer
     /**
      * Take value and turn it into a string suitable for inclusion in
      * the http body (form parameter). If it's a string, pass through unchanged
-     * If it's a datetime object, format it in RFC3339
+     * If it's a datetime object, format it in ISO8601
      *
      * @param string|\SplFileObject $value the value of the form parameter
      *
@@ -156,18 +161,16 @@ class ObjectSerializer
     /**
      * Take value and turn it into a string suitable for inclusion in
      * the parameter. If it's a string, pass through unchanged
-     * If it's a datetime object, format it in RFC3339
-     * If it's a date, format it in Y-m-d
+     * If it's a datetime object, format it in ISO8601
      *
      * @param string|\DateTime $value the value of the parameter
-     * @param string|null $format the format of the parameter
      *
      * @return string the header string
      */
-    public static function toString($value, $format = null)
+    public static function toString($value)
     {
-        if ($value instanceof \DateTime) {
-            return ($format === 'date') ? $value->format('Y-m-d') : $value->format(\DateTime::ATOM);
+        if ($value instanceof \DateTime) { // datetime in ISO8601 format
+            return $value->format(\DateTime::ATOM);
         } else {
             return $value;
         }
@@ -276,7 +279,7 @@ class ObjectSerializer
 
             return new \SplFileObject($filename, 'r');
         } elseif (method_exists($class, 'getAllowableEnumValues')) {
-            if (!in_array($data, $class::getAllowableEnumValues())) {
+            if (!in_array($data, $class::getAllowableEnumValues(), true)) {
                 $imploded = implode("', '", $class::getAllowableEnumValues());
                 throw new \InvalidArgumentException("Invalid value for enum '$class', must be one of: '$imploded'");
             }
diff --git a/src/main/resources/handlebars/php/api_test.mustache b/src/main/resources/handlebars/php/api_test.mustache
index b2561cfe89..c381754766 100644
--- a/src/main/resources/handlebars/php/api_test.mustache
+++ b/src/main/resources/handlebars/php/api_test.mustache
@@ -21,6 +21,7 @@ namespace {{invokerPackage}};
 use {{backslash}}{{invokerPackage}}\Configuration;
 use {{backslash}}{{invokerPackage}}\ApiException;
 use {{backslash}}{{invokerPackage}}\ObjectSerializer;
+use PHPUnit\Framework\TestCase;
 
 /**
  * {{classname}}Test Class Doc Comment
@@ -30,37 +31,38 @@ use {{backslash}}{{invokerPackage}}\ObjectSerializer;
  * @author   Swagger Codegen team
  * @link     https://github.com/swagger-api/swagger-codegen
  */
-{{#operations}}class {{classname}}Test extends \PHPUnit_Framework_TestCase
+{{#operations}}class {{classname}}Test extends TestCase
 {
 
     /**
      * Setup before running any test cases
      */
-    public static function setUpBeforeClass()
+    public static function setUpBeforeClass(): void
     {
     }
 
     /**
      * Setup before running each test case
      */
-    public function setUp()
+    public function setUp(): void
     {
     }
 
     /**
      * Clean up after running each test case
      */
-    public function tearDown()
+    public function tearDown(): void
     {
     }
 
     /**
      * Clean up after running all test cases
      */
-    public static function tearDownAfterClass()
+    public static function tearDownAfterClass(): void
     {
     }
     {{#operation}}
+    {{#contents}}
 
     /**
      * Test case for {{{operationId}}}
@@ -68,9 +70,10 @@ use {{backslash}}{{invokerPackage}}\ObjectSerializer;
      * {{{summary}}}.
      *
      */
-    public function test{{vendorExtensions.x-testOperationId}}()
+    public function test{{vendorExtensions.x-testOperationId}}{{#isForm}}Form{{/isForm}}()
     {
     }
+    {{/contents}}
     {{/operation}}
 }
 {{/operations}}
diff --git a/src/main/resources/handlebars/php/composer.mustache b/src/main/resources/handlebars/php/composer.mustache
index 0a7732fafe..1d9038cf7d 100644
--- a/src/main/resources/handlebars/php/composer.mustache
+++ b/src/main/resources/handlebars/php/composer.mustache
@@ -8,6 +8,7 @@
         "swagger",
         "php",
         "sdk",
+        "rest",
         "api"
     ],
     "homepage": "http://swagger.io",
@@ -19,16 +20,16 @@
         }
     ],
     "require": {
-        "php": ">=5.5",
+        "php": "^7.4 || ^8.0",
         "ext-curl": "*",
         "ext-json": "*",
         "ext-mbstring": "*",
-        "guzzlehttp/guzzle": "^6.2"
+        "guzzlehttp/guzzle": "^7.3",
+        "guzzlehttp/psr7": "^1.7 || ^2.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "^4.8",
-        "squizlabs/php_codesniffer": "~2.6",
-        "friendsofphp/php-cs-fixer": "~1.12"
+        "phpunit/phpunit": "^8.0 || ^9.0",
+        "friendsofphp/php-cs-fixer": "^3.5"
     },
     "autoload": {
         "psr-4": { "{{escapedInvokerPackage}}\\" : "{{srcBasePath}}/" }
diff --git a/src/main/resources/handlebars/php/model_generic.mustache b/src/main/resources/handlebars/php/model_generic.mustache
index ca67203013..be1beb0983 100644
--- a/src/main/resources/handlebars/php/model_generic.mustache
+++ b/src/main/resources/handlebars/php/model_generic.mustache
@@ -166,7 +166,7 @@ class {{classname}} {{#parentSchema}}extends {{{parent}}} {{/parentSchema}}{{^pa
         {{#discriminator}}
 
         // Initialize discriminator property with the model name.
-        $discriminator = array_search('{{discriminator.propertyName}}', self::$attributeMap);
+        $discriminator = array_search('{{discriminator.propertyName}}', self::$attributeMap, true);
         $this->container[$discriminator] = static::$swaggerModelName;
         {{/discriminator}}
     }
@@ -353,7 +353,7 @@ class {{classname}} {{#parentSchema}}extends {{{parent}}} {{/parentSchema}}{{^pa
      *
      * @return boolean
      */
-    #[\ReturnTypeWillChange] 
+    #[\ReturnTypeWillChange]
     public function offsetExists($offset)
     {
         return isset($this->container[$offset]);
@@ -366,7 +366,7 @@ class {{classname}} {{#parentSchema}}extends {{{parent}}} {{/parentSchema}}{{^pa
      *
      * @return mixed
      */
-    #[\ReturnTypeWillChange] 
+    #[\ReturnTypeWillChange]
     public function offsetGet($offset)
     {
         return isset($this->container[$offset]) ? $this->container[$offset] : null;
@@ -380,7 +380,7 @@ class {{classname}} {{#parentSchema}}extends {{{parent}}} {{/parentSchema}}{{^pa
      *
      * @return void
      */
-    #[\ReturnTypeWillChange] 
+    #[\ReturnTypeWillChange]
     public function offsetSet($offset, $value)
     {
         if (is_null($offset)) {
@@ -397,7 +397,7 @@ class {{classname}} {{#parentSchema}}extends {{{parent}}} {{/parentSchema}}{{^pa
      *
      * @return void
      */
-    #[\ReturnTypeWillChange] 
+    #[\ReturnTypeWillChange]
     public function offsetUnset($offset)
     {
         unset($this->container[$offset]);
diff --git a/src/main/resources/handlebars/php/model_test.mustache b/src/main/resources/handlebars/php/model_test.mustache
index 99064308f5..f96884d1db 100644
--- a/src/main/resources/handlebars/php/model_test.mustache
+++ b/src/main/resources/handlebars/php/model_test.mustache
@@ -21,6 +21,8 @@
 
 namespace {{invokerPackage}};
 
+use PHPUnit\Framework\TestCase;
+
 /**
  * {{classname}}Test Class Doc Comment
  *
@@ -30,34 +32,34 @@ namespace {{invokerPackage}};
  * @author      Swagger Codegen team
  * @link        https://github.com/swagger-api/swagger-codegen
  */
-class {{classname}}Test extends \PHPUnit_Framework_TestCase
+class {{classname}}Test extends TestCase
 {
 
     /**
      * Setup before running any test case
      */
-    public static function setUpBeforeClass()
+    public static function setUpBeforeClass(): void
     {
     }
 
     /**
      * Setup before running each test case
      */
-    public function setUp()
+    public function setUp(): void
     {
     }
 
     /**
      * Clean up after running each test case
      */
-    public function tearDown()
+    public function tearDown(): void
     {
     }
 
     /**
      * Clean up after running all test cases
      */
-    public static function tearDownAfterClass()
+    public static function tearDownAfterClass(): void
     {
     }