ReadonlyPropertyAssignment

A readonly property is assigned after the constructor.

Example

<?php
class User {
    public readonly string $name;

    public function __construct(string $name) {
        $this->name = $name;
    }

    public function rename(string $name): void {
        $this->name = $name; // not allowed after construction
    }
}

How to fix

Remove the post-construction assignment; readonly properties can only be set once during construction.