$re = '/(?(DEFINE) # start DEFINE block
# pre-define quant subroutine
(?<quant>many|some|five)
# pre-define adj subroutine
(?<adj>blue|large|interesting)
# pre-define object subroutine
(?<object>cars|elephants|problems)
# pre-define noun_phrase subroutine
(?<noun_phrase>(?&quant)\ (?&adj)\ (?&object))
# pre-define verb subroutine
(?<verb>borrow|solve|ressemble)
) # end DEFINE block
##### The regex matching starts here #####
(?&noun_phrase)\ (?&verb)\ (?&noun_phrase)/x';
$str = 'five blue elephants solve many interesting problems
many large problems ressemble some interesting cars';
preg_match_all($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