$re = '/(?s)([A-G][1-3])((?:(?![A-G][1-3]).)*)/';
$str = 'A1 ACBFEKJRQ0Z+-F2.,12STLMGHDF19)(D2!?56WXPC1IONVU43\\"\\\'E1Y87><A3-=.,\\\'\\"!?><()@';
preg_match_all($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