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ImplementedReturnTypeMismatch

Emitted when a class that inherits another, or implements an interface, has a docblock return type that's entirely different to the parent.

<?php

class A {
    /** @return bool */
    public function foo() {
        return true;
    }
}
class B extends A {
    /** @return string */
    public function foo()  {
        return "hello";
    }
}

How to fix

Make sure to respect the Liskov substitution principle – any method that overrides a parent method must return a subtype of the parent method.

In the above case, that means adding the child return type to the parent one.

<?php

class A {
    /** @return bool|string */
    public function foo() {
        return true;
    }
}
class B extends A {
    /** @return string */
    public function foo()  {
        return "hello";
    }
}