Cannot use the %s modifier on a %s¶

Description¶

This is a generic error message for cases where a keyword cannot be used with a class structure. For example, a class constant cannot be abstract or static.

A special case is using final on a parameter: final is reserved for properties, although properties may be promoted, and also used as a parameter in a constructor. Then, it is not possible to declare the property final, or in the constructor.

final for class constant was also unavailable in PHP 8.0, and it is now a feature.

Example¶

<?php

class X {
    private final const A = 1;
    private abstract const B = 1;
    private static const C = 1;

    function __construct (
        final public $p = 1
    ) {}
}


?>

Literal Examples¶

Cannot use the final modifier on a class constant
Cannot use the abstract modifier on a class constant
Cannot use the static modifier on a class constant
Cannot use the final modifier on a parameter

Solutions¶

Remove the option from the class constant definition.
Upgrade to PHP 8.1 or later, for final on class constants.