$re = '/^(?:(?=.*?[A-Z])(?:(?=.*?[0-9])(?=.*?[-!@#$%^&*()_[\]{},.<>+=])|(?=.*?[a-z])(?:(?=.*?[0-9])|(?=.*?[-!@#$%^&*()_[\]{},.<>+=])))|(?=.*?[a-z])(?=.*?[0-9])(?=.*?[-!@#$%^&*()_[\]{},.<>+=]))[A-Za-z0-9!@#$%^&*()_[\]{},.<>+=-]{7,50}$/mx';
$str = ' 1 2 3 4 5 6
12345678901234567890123456789012345678901234567890124567890
aaaaAAAA1111
aaaaBBBBBBB
AAAAaaaa__
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa!A
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa!
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa!A
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa!AA
';
preg_match_all($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