$re = '/(?i)^(?!.{16})^.+[.](?:asf|avi|csv|pdf|doc|docx|dot|eml|gif|htm|html|idx|tif|jpg|jpeg|bmp|png|mp3|mpg|msg|ppt|pptx|pst|rtf|txt|wav|wma|xls|xlsx|zip)$/m';
$str = '12345678901.jpg';
preg_match_all($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