3v4l.org

run code in 300+ PHP versions simultaneously
<?php list($x,$y) = microtime(); $a = ''; for($i=0; $i<1000000; $i++) $a = 'yay'; $t = microtime(true); echo round((($n+$p)-$x-$y)*1000); list($x,$y) = microtime(); $a = ''; for($i=0; $i<1000000; $i++) $a = "yay"; echo round(microtime(true)-$t);

preferences:
36.62 ms | 402 KiB | 5 Q