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<?php declare(strict_types=1); interface I { public function example(); } class A implements I { public function example(): int { return 123; } // compatible with I::example } class B extends A { public function example(): string { return "string"; } // compatible with I::example } function accepts_i_expects_any(I $i) { var_dump($i->example()); } accepts_i_expects_any(new B); // receives string, no problem function accepts_a_expects_int(A $a) { var_dump($a->example()); } accepts_a_expects_int(new B); // receives string, problem
Output for 7.4.0 - 7.4.22, 8.0.0 - 8.0.8
Fatal error: Declaration of B::example(): string must be compatible with A::example(): int in /in/TUbfJ on line 12
Process exited with code 255.
Output for 7.2.0 - 7.2.33, 7.3.0 - 7.3.29
Fatal error: Declaration of B::example(): string must be compatible with A::example(): int in /in/TUbfJ on line 11
Process exited with code 255.
Output for 7.0.0 - 7.0.20, 7.1.1 - 7.1.25
string(6) "string" string(6) "string"
Output for 7.1.0

Process exited with code 137.

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