$re = '/^(?=[a-z0-9!@#$%^&*()+=?]*[A-Z])(?=[A-Z0-9!@#$%^&*()+=?]*[a-z])[A-Za-z0-9!@#$%^&*()+=?]*$/m';
$str = 'aB123!
a123!
123A!
Ab123{
';
preg_match_all($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