php - Mvc Method name must be a string -

i have problem , dont have idea how slove this.

problem on line code:

   public function executeaction() {         return $this->{$this->action}();     } 

all other work fine controller success loaded have fatal error this.

fatal error: method name must string in d:\xampp\htdocs\workplace\mvc\lib\basecontroller.php on line 27

check code:

index.php

$fcontroller = new fcontroller($_get); $controller = $fcontroller->createcontroller(); $controller->executeaction(); 

fcontorler

   public function createcontroller()     {         if(class_exists($this->controller)) {             $parent = class_parents($this->controller);             if(in_array('basecontroller', $parent)) {                 if(method_exists($this->controller, $this->action)) {                     return new $this->controller($this->action, $this->url);                 }else {                     echo "method no exists";                 }             }else {                 echo "bad controller";             }         } else {             echo "controller ". $this->controller . " class no exists";         }    } 

basecontroller

abstract class basecontroller {      protected $urlvalues;     protected $action;      /*      * construct      *       * @param string  $action      * @param array   $url      *       */      public function __construct($action, $urlvalues) {         $this->action = $action;         $this->urlvalues = $urlvalues;     }      /*      * execute acction      *       */      public function executeaction() {         return $this->{$this->action}();     } 

localhost/workplace/mvc/index.php?controller=hello&action=say&id=5

var_dump($controller); object(hello)#2 (2) { ["urlvalues":protected]=> null ["action":protected]=> null }

the error triggered because trying use null while interpreter expecting string.

as var_dump shows, $this->action null therefore string interpolation $this->{$this->action}(); translated $this->{null}(); cannot called.