$re = '/(^\w+$\n?){20,}/m';
$str = 'property
subject
recipe
newsletter
news
match
reply
bulletin
joke
annual
greeting
accepted
puzzle
march
meeting
din
order
alert
printer
thursday
case
chicago
member';
preg_match($re, $str, $matches, PREG_OFFSET_CAPTURE, 0);
// Print the entire match result
var_dump($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