Constants Are Mutable

<?php
  
class x {
    public string $p = 'abc';
}

const A = new x;

A->p = 'def';

echo A->p; // def

?>

Since PHP 8.2, it is possible to use an object with a constant: this is the new initializer feature.

With a object in a constant, it is still possible to call methods or properties, and mutate the constants. Indeed, the constant is still representing the same object, but the properties in the objects are not constants.

See Also

• Class Constants
• Constants are no longer constant in PHP
• How To Alter A Constant [Try me]

PHP Features

• constant
• new-in-initializer
• object

Last updated: 10 September 2026