3v4l.org

run code in 300+ PHP versions simultaneously
<?php function isQuadtree($bits, &$i = 0){ if ($i >= str_length($bits)) return false; if ($bits[$i] === "1") { isQuadtree($bits, $i++); isQuadtree($bits, $i++); isQuadtree($bits, $i++); return isQuadtree($bits, $i++); } return true; }
Output for 8.1.34, 8.2.27 - 8.2.30, 8.3.0 - 8.3.29, 8.4.1 - 8.4.16, 8.5.0 - 8.5.1

preferences:
29.53 ms | 406 KiB | 5 Q