Online PHP editor | output for l1dlE

<?php declare(strict_types = 1); function select1(int $offset = 0) { var_dump($offset); } function select2(?int $offset = 0) { var_dump($offset); } function select3(int $offset = null) { var_dump($offset); } function select4(?int $offset = null) { // same as select3 var_dump($offset); } select1(); select1(0); // select1(null); // <------ fails select2(); select2(0); select2(null); select3(); select3(0); select3(null); select4(); select4(0); select4(null);