update php samples

samples/client/echo_api/php-nextgen/src/Model/ModelInterface.php

@@ -42,49 +42,49 @@ interface ModelInterface
      *
      * @return string
      */
-    public function getModelName();
+    public function getModelName(): string;
 
     /**
      * Array of property to type mappings. Used for (de)serialization
      *
      * @return array
      */
-    public static function openAPITypes();
+    public static function openAPITypes(): array;
 
     /**
      * Array of property to format mappings. Used for (de)serialization
      *
      * @return array
      */
-    public static function openAPIFormats();
+    public static function openAPIFormats(): array;
 
     /**
      * Array of attributes where the key is the local name, and the value is the original name
      *
      * @return array
      */
-    public static function attributeMap();
+    public static function attributeMap(): array;
 
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
      * @return array
      */
-    public static function setters();
+    public static function setters(): array;
 
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
      * @return array
      */
-    public static function getters();
+    public static function getters(): array;
 
     /**
      * Show all the invalid properties with reasons.
      *
      * @return array
      */
-    public function listInvalidProperties();
+    public function listInvalidProperties(): array;
 
     /**
      * Validate all the properties in the model
@@ -92,7 +92,7 @@ interface ModelInterface
      *
      * @return bool
      */
-    public function valid();
+    public function valid(): bool;
 
     /**
      * Checks if a property is nullable