@readonly

The @readonly tag declares that a property may only be written once, during initialization, and must not change afterwards. It is the documentation-level equivalent of PHP's native readonly property modifier, used where the native modifier cannot be applied — most commonly on magic or virtual properties exposed through __get/__set and documented with @property rather than declared as real class members.

Parsing a @readonly tag produces a ReadonlyTag instance. Being a pure marker, it adds nothing beyond the $name and optional $description every Tag already carries.

Unlike most tags in this reference, @readonly is not part of the PSR-19 draft or phpDocumentor's own tag list. Psalm and PHPStan each ship their own independent support for it — distinct from PHP 8.1's native readonly property modifier that inspired its name. See Psalm's @readonly documentation and PHPStan's PHPDoc basics guide.