PHP Fatal error: Cannot use $this as parameter

Question

I\'ve the following PHP method which is part of the codebase which was working fine:

Answer 1

If you want it to work the same way it did before, you should not remove $this as a parameter. You should change the name of the parameter to something else, and change the corresponding variable name in the closure.

Through PHP 5.6, using $this as a parameter in a closure in a class method would mask the $this referring to the parent object. For example:

class Example
{
    public function test ($param) {
        $closure = function ($whatever) {      // $this not used as parameter
            return $this;                      // $this refers to the Example object
        };
        return $closure($param);
    }

    public function test2 ($param) {
        $closure = function($this) {          // $this used as parameter
            return $this;                     // $this no longer refers to Example object
        };
        return $closure($param);
    }

}

$ex = new Example;
$not_masked = $ex->test('foo');
$masked = $ex->test2('foo');

var_dump($not_masked, $masked);

Working example on 3v4l.org

In PHP 5.6, $masked would be the string 'foo', not the $ex object.

According to the output for the different versions that you can see at the 3v4l.org link, there was a brief period from 7.0.0-7.0.6 where the $this parameter would apparently be disregarded in favor of the object self-reference. I assume they disallowed using $this as a parameter in later versions to avoid the ambiguity of what $this actually referred to in the closure scope.

It looks like this was just confusing naming in the original code. In order to make it work as before:

->andReturnUsing(function ($anyOtherName) {
    return $anyOtherName;
});