mixed Is Not No Type

<?php

class x {
    public $p;
    public mixed $q;
}

$x = new x;
var_dump($x->p);
var_dump($x->q);  // Fatal error!

When a property is not typed, nor has a default value, it still may be accessed freely: its value is null. On the other hand, a mixed typed property may also hold anything, but it cannot be accessed until it was written once.

On development, it might be a good strategy to type properties mixed to spot any uninitialized usage and set them.

See Also

• mixed (PHP manual)
• mixed is not absence of type [Try me]

PHP Error Messages

• Typed property %s::$%s must not be accessed before initialization

PHP Features

• mixed
• type
• initialisation

Last updated: 10 September 2026