Reason for Undefined class constant NOTICE in PHP (Use of undefined constant)

Question

I have discovered a weird problem in my code regarding class constants. While it seems that the code does work correctly, I cannot figure out the reason of PHP Notice I am getting:

Use of undefined constant PAYMENT_ERROR - assumed 'PAYMENT_ERROR' in /src/Micro/Payments/Manager.php on line 146

The code in Manager.php function looks like this:

$code = Result::PAYMENT_ERROR;
return new Result($code, $errMsg); // <- line 146 - causes PHP Notice

What is strange to me, is that $code variable is set correctly and does not trigger any notices. Only instantiating Result does.

The Result class is very simple:

class Result
{
    // ... boilerplate code skipped ...
    // constant is defined like this:
    const PAYMENT_ERROR = 2;

    public function __construct($code, array $messages)
    {
        $this->code = $code;
        $this->messages = $messages;
    }

    // ... other functions skipped as they are not relevat ...
}

Is there a problem that I pass Result's constant to it's own constructor?

Answer 1

I have found the reason for this notice and fixed it.

I have had this line in Result class:

protected $code = PAYMENT_ERROR;

This was causing the notice above, as I did not define this correctly. I would have expected PHP to tell me where the error message was coming from exactly, when instantiating new Class, instead of just pointing to a line where said Class is instaniated.

So the fix was to change it to this:

protected $code = self::PAYMENT_ERROR;