$re = '/casenumber(\s*[^\s\d]+\s*\d{7,8})+/';
$str = 'Hi!
Hereby I would like to confirm that I will be present at the meeting about casenumber: 1234567 and 7654321.
Can you confirm that you have received this email?
Kind regards,
Random person';
preg_match_all($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