3v4l.org

run code in 300+ PHP versions simultaneously
<?php $str = "1111 2222 3333 4444 5555 6666"; if (preg_match('~\A(?:\d{4}\s?)+\z~', $str)) { print_r(preg_split('~\s~', $str)); }

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53.46 ms | 402 KiB | 5 Q