Invalid operation causes constant expression to be invalid

Question

I have the following code and when I define a variable in the constructor I get the error "PHP Fatal Error: Constant expression contains an invalid operation". It works fine when used in Laravel framework.

<?php

namespace App;

class Amazon
{
    protected $serviceURL = config('api.amazon.service_url');

    public function __construct()
    {
    }

}

I saw this question: PHP error: fatal error: constant expression contains an invalid operation But my code doesn't declare any static content, so this answer doesn't solve my problem.

Answer 1

This method does not allow initialization of class attributes. You have to move the initialization into the constructor.

Answer 2

As described here

The only way you can make it work is:

<?php

namespace App;

class Amazon
{
  protected $serviceURL;

  public function __construct()
  {
    $this->serviceURL = config('api.amazon.service_url');
  }
}