$re = '/\b[\d\-\/@#$]{12}\b/';
$str = '18129561-000
asdf 1812956-1-000 asd
asdf 18129562-000 asd
asd18129561-000as
18129561@000';
preg_match_all($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