$re = '/\d\d[A-Z]?(?:\s*(?:and|or|,)\s*\d\d[A-Z]?)*/mx';
$str = 'biscuits 10 are good
biscuits 20 and 30 are good
biscuits 40 and hot dog are good
but this one 50A and 50B and not ok';
preg_match_all($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