函数数组作为对象的私有属性

Question

I would like to know the reason of "Unexpected T_FUNCTION" error in this php code:

class T
{
    private $array_of_functions = array(
        '0' => function() { return true; }
    );
}

Answer 1

You can not use such construction as default property value. Default property value can be only constant expression - so it can not contain closure definition since it's dynamic (i.e. evaluated when constructed at runtime). Instead you should initialize it inside class constructor:

class T
{
   private $array_of_functions = [];

   public function __construct()
   {
      $this->array_of_functions = [
         function() { return true; }
      ];
   }
}