3v4l.org

run code in 300+ PHP versions simultaneously
<?php function is_hex($hex_code) { return @preg_match("/^[a-f0-9]{2,}$/i", $hex_code) && !(strlen($hex_code) & 1); } var_dump(is_hex("A0b"));

preferences:
41.65 ms | 402 KiB | 5 Q