No Final Parameter

<?php

class X {
    function __construct(
        //Cannot use the final modifier on a parameter        
        private final $property
    ) {}
}

Final is reserved for class elements, such as property, methods and constants. They do not apply to parameters, unless the parameter is a promoted property, in the constructor signature.

In that case, the property cannot be declared in the constructor, and must be declared independently, or without the final key word.

See Also

• Final (PHP manual)
• Final On A Parameter [Try me]

PHP Error Messages

• Cannot use the %s modifier on a %s

PHP Features

• final
• promoted-property
• parameter

Last updated: 10 September 2026