$re = '/x\([^8\s]*8[^8\s]*\)/';
$str = '39x(7,8)
3x(8)
2x(8,1)
3x(8,9)
1x(11)
3x(11,7,8)
11x(11,7,8,9)
11x(11,7,88,9)
31x(11,7,8,9,10)
1x(11,7,8,9,10,12)
2x(7,8,10)
224x(7,8,9)
31x(11,7,8,9,10)
1x(11,7,9,10,12)
2x(7,8,10)
224x(7,8,9)
13x(7,8,9,10)';
preg_match_all($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