$re = '/"[a-zA-Z][1-9]@[gmail].com"/m';
$str = '2[23 3] + [1 22 3] + 7
[2] + [12351]
12[45 12]
[56]
[2] + 1 + [2]
2[2 a]
1[2 3 4] + []
3[2 3 4] + a[1 2 3]
3[2 3 4] +';
preg_match_all($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