Fatal error: Constant expression contains invalid operations in C: \ xampp \ htdocs \ test \ php_tests \ app \ controller \ auth \ Token.php on line 18

  

Fatal error: Constant expression contains invalid operations in   C: \ xampp \ htdocs \ test \ php_tests \ app \ controller \ auth \ Token.php on   line 18

protected $token = [

        'csrf' => random_int(0, 500) // line 18
    ];

Good that is the error that jumps me. I need that space to generate a random number but I get an error