$re = '/\bin stock\b|(?:\s+|^)((?:(?!\b(?:notify|not in stock|in stock)\b).)+\b(?:notify|not in stock)\b)/m';
$str = 'item1 120usd not in stock item2 150usd in stock item3 100usd notify item4 12usd in stock item5 25usd not in stock item6 250usd notify item7 50usd in stock item8 30sud in stock item9 5usd notify item10 5usd notify';
preg_match_all($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