PHP: ArgumentCountError on method with optional parameter

Question

PHP 8.1. I declared a method with this signature:

public static function if(mixed $condition, mixed $subject = null, \Closure $callback)

And called it with this call:

CLASS::if(condition: is_numeric(...), callback: do_something(...));

Yet I still got this exception:

ArgumentCountError: CLASS::if(): Argument #2 ($subject) not passed

Why? $subject clearly is set to default to null.

php function's required parameter confusion and Required parameter $xxx follows optional parameter $yyy — mickmackusa
– mickmackusa ♦, Commented Dec 5, 2023 at 22:52
Simple demo of breakge: 3v4l.org/D4HhA and after fixing the method signature: 3v4l.org/agWnE — mickmackusa
– mickmackusa ♦, Commented Dec 5, 2023 at 23:06

Blackhole · Accepted Answer · 2023-12-05 22:44:51Z

1

Since the $callback parameter has no default value, it's a required argument, and so is every argument before it. Therefore, $subject = null doesn't mean null is a default value; it only means $subject is nullable (everything other than null would have triggered a deprecation notice).

To solve the problem, depending on the behaviour you're expecting, you can either place the $subject parameter at the end, or add a default value to the $callback parameter.

edited Dec 5, 2023 at 22:44

answered Dec 5, 2023 at 22:40

Blackhole

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1 Comment

mickmackusa Over a year ago

If you feel that one of the links that I commented is a suitable dupe target, please vote to close and transfer your advice there because stackoverflow.com/help/….

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