3v4l.org

run code in 300+ PHP versions simultaneously
<?php $a = array('a', 'b', 'c', 'd', null); for($i = 0; $i < count($a); $i += 2) { echo $i . " "; if (array_key_exists($i + 1, $a)) { echo $a[$i + 1] . " "; } echo ($i + 1) . PHP_EOL; }
Output for 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.27, 8.2.0 - 8.2.17, 8.3.0 - 8.3.4
0 b 1 2 d 3 4 5

preferences:
202.74 ms | 403 KiB | 284 Q