$re = '/^(?!(?=[a-f\d]{24}$)(\d+[a-f]|[a-f]+\d)).+/mi';
$str = '112345679065574883030833
FFFFFFFFFFFFFFFFFFFFFFFF
45cbc4a0e4123f6920000002
112345679065574883030833
James Bond';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php