Asymmetric Visibility

Asymmetric visibility is a feature of PHP class properties. They refer to the situation where different scopes may read, or get or write, or set.

Traditionally, the visibility options, private, protected and public, constraints the access to the property, both in reading and writing. With asymmetric visibility, there may be contexts may have different rights of access.

<?php

class X {
    public private(set) string $p = 'abc';

    function setP($p) {
        $this->p = $p;
    }
}

$x = new X();
echo $x->p; // abc
$x->setP('def');
echo $x->p; // def

//
$x->p = 'ghi';

?>

See also PHP Asymmetric Visibility RFC: An In-Depth Look and New in PHP 8.5: Asymmetric Visibility for Static Properties.

Related : Visibility, Properties, Asymmetric Property, Property Type Declaration, Var