$re = '/(?:\d\s*){5}\d/';
$str = '1 23456
1 2 3456
1 2 3 456
1 2 3 4 56
1 2 3 4 5 6';
preg_match_all($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