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run code in 300+ PHP versions simultaneously
<?php abstract class A { public abstract function run(): mixed; } class B extends A { public function run() { } }
Output for 7.4.0 - 7.4.30, 8.0.1 - 8.0.21, 8.1.0 - 8.1.8
Fatal error: Declaration of B::run() must be compatible with A::run(): mixed in /in/i8EK4 on line 10
Process exited with code 255.

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