$re = ';(?<prefix1>\d{0,3}?)(?<threes1>\d{1,3})\/(?<prefix2>\d{0,3})(?<threes2>\d{3});';
$str = '1/1
12/1
123/1
1234/1
12345/1
123456/1
1/12
1/123
1/1234
1/12345
1/123456
12/12
123/12
1234/12
12345/12
123456/12
12/123
12/1234
12/12345
12/123456
123/123
1234/123
12345/123
123456/123
123/1234
123/12345
123/123456
1234/1234
12345/1234
123456/1234
1234/12345
1234/123456
12345/12345
123456/12345
12345/123456
123456/123456
';
preg_match_all($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