3v4l.org

run code in 300+ PHP versions simultaneously
<?php $phone = preg_replace("/[^0-9]/", "", "600000005"); echo strlen(strval($phone)); if (strlen(strval($phone)) < 10) { echo "0$phone"; } else { echo strval($phone); }

preferences:
64.87 ms | 402 KiB | 5 Q