$re = '/(.)(?:(?:0(?=1|\b)|1(?=2|\b)|2(?=3|\b)|3(?=4|\b)|4(?=5|\b)|5(?=6|\b)|6(?=7|\b)|7(?=8|\b)|8(?=9|\b)|9(?=0|\b)){3,})/';
$str = '123';
preg_match_all($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