Readonly property %s::$%s must have type

Description

A readonly property must be typed. It cannot be left without a type. In case of need of a wide range of types, use an union type, or the mixed keyword.

Example

<?php

class X {
    private readonly $property;
}

?>

Literal Examples

  • Readonly property X::$property must have type

Solutions

  • Use the mixed type to explicitly type the property, but not commit to any constraint.

  • Use an union type to explicitly type the property, and commit to a restricted list of types.

  • Use the actual type for the property.

  • Remove the readonly option.

Static Analysis

This error may be tracked down with the following static analysis rules: Classes/ReadonlyCompatibility.