$re = '/\b(?:north|south)(?:\h*(?:east|west))?\b|\b(?:east|west|[NS][WE]?|[EW])\b/i';
$str = 'SHOULD MATCH:
405 W 1st Street South west #910
North, South, West, East, North East, North West, South East, South West
N, S, NW, NE, SE, SW, E, W.
northeast northwest southeast southwest
PARTIAL MATCH:
north-west north-east south-west south-east
SHOULD NOT MATCH:
westnorth westsouth eastnorth eastsouth
wn ws en es
';
preg_match_all($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