$re = '/^(last|previous|next|down)(.*?)(word[s]?|line[s]?|sentence[s]?|paragraph[s]?|para[s]?|char[s]?|character[s]?|space|\n\n|\n)$/m';
$str = 'previous2word
last5paras
next10characters
lastspace';
preg_match_all($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