fix(php): fix typo

Author: damcou

templates/php/ObjectSerializer.mustache

@@ -56,22 +56,22 @@ class ObjectSerializer
             $values = [];
             if ($data instanceof ModelInterface) {
                 $formats = $data::modelFormats();
-                foreach ($data::openAPITypes() as $property => $openAPIType) {
+                foreach ($data::modelTypes() as $property => $modelTypes) {
                     $getter = $data::getters()[$property];
                     $value = $data->$getter();
-                    if ($value !== null && !in_array(modelTypes, [{{{primitives}}}], true)) {
-                        $callable = [modelTypes, 'getAllowableEnumValues'];
+                    if ($value !== null && !in_array($modelTypes, [{{{primitives}}}], true)) {
+                        $callable = [$modelTypes, 'getAllowableEnumValues'];
                         if (is_callable($callable)) {
                             /** array $callable */
                             $allowedEnumTypes = $callable();
                             if (!in_array($value, $allowedEnumTypes, true)) {
                                 $imploded = implode("', '", $allowedEnumTypes);
-                                throw new \InvalidArgumentException("Invalid value for enum 'openAPITypes', must be one of: '$imploded'");
+                                throw new \InvalidArgumentException("Invalid value for enum '$modelTypes', must be one of: '$imploded'");
                             }
                         }
                     }
                     if ($value !== null) {
-                        $values[$data::attributeMap()[$property]] = self::sanitizeForSerialization($value, openAPITypes, $formats[$property]);
+                        $values[$data::attributeMap()[$property]] = self::sanitizeForSerialization($value, $modelTypes, $formats[$property]);
                     }
                 }
             } else {