$re = '/^([sS][gG][1|4]|[aA][lL][6-7|10|2-3]|[wW][dD][23|25|7|4]|[hH][pP][1|3-4]|[lL][uU]1)\d?\b/m';
$str = 'SG1
SG4
AL2
AL6
AL7
AL10
WD4
WD7
WD23
WD25
HP1
HP3
HP4
LU1';
preg_match_all($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