Online PHP editor | output for Q2H2Z

<?php function foo(int $a) { var_dump($a); } function define_callbacks() { $string = 'foo'; $lambda = fn(...$args) => foo(...$args); $fcc = foo(...); return [$string, $lambda, $fcc]; } function test_callback($callback) { $callback(1); try { $callback(new class{}); } catch ( TypeError $e ) { echo $e->getMessage(), "\n"; } } [$string, $lambda, $fcc] = define_callbacks(); echo "== String-based ==\n"; test_callback($string); echo "\n== Type-less lambda ==\n"; test_callback($lambda); echo "\n== First-class callable ==\n"; test_callback($fcc);