ReadonlyPropertyRedeclarationMismatch

A readonly property in a child class conflicts with the parent’s declaration, such as redeclaring a non-readonly property as readonly or vice versa.

Example

<?php
class Parent {
    public string $name;
}

class Child extends Parent {
    public readonly string $name; // Error: cannot change readonly modifier
}

How to fix

Maintain consistent readonly modifiers across the inheritance hierarchy:

<?php
class Parent {
    public readonly string $name;
}

class Child extends Parent {
    // Keep the same readonly modifier
    public readonly string $name;
}