3v4l.org

run code in 500+ PHP versions simultaneously
<?php $stop = microtime(true) + 1; $i = 0; while(microtime(true) < $stop){ if(++$i % 1000000 == 0){ echo $i / 1000000, "<br/>\n"; } } echo "done.<br/>\n";

preferences:
52.68 ms | 703 KiB | 5 Q