[PHP] Correctly serialize php arrays

Use json_encode for php arrays, so they can be used as the root type in a json request body.

Author: christiaanderidder

modules/swagger-codegen/src/main/resources/php/api.mustache

@@ -426,9 +426,16 @@ use {{invokerPackage}}\ObjectSerializer;
         if (isset($_tempBody)) {
             // $_tempBody is the method argument, if present
             $httpBody = $_tempBody;
-            // \stdClass has no __toString(), so we should encode it manually
-            if ($httpBody instanceof \stdClass && $headers['Content-Type'] === 'application/json') {
-                $httpBody = \GuzzleHttp\json_encode($httpBody);
+            
+            if($headers['Content-Type'] === 'application/json') {
+                // \stdClass has no __toString(), so we should encode it manually
+                if ($httpBody instanceof \stdClass) {
+                    $httpBody = \GuzzleHttp\json_encode($httpBody);
+                }
+                // array has no __toString(), so we should encode it manually
+                if(is_array($httpBody)) {
+                    $httpBody = \GuzzleHttp\json_encode(ObjectSerializer::sanitizeForSerialization($httpBody));
+                }
             }
         } elseif (count($formParams) > 0) {
             if ($multipart) {