$re = '/\b(?:[0-9],[1-9][0-9]+|0,[1-9]|1,[2-9]|2,[3-9]|3,[4-9]|4,[5-9]|5,[6-9]|6,[7-9]|7,[8-9]|8,9)\b/';
$str = '7,10
5,3
0,1
8,9
0,20
10,20
21,12
1,12';
preg_match_all($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