$re = '/^([A-PR-UWYZ](([0-9](([0-9]|[A-HJKSTUW])?)?)|([A-HK-Y][0-9]([0-9]|[ABEHMNPRVWXY])?)) ?[0-9][ABD-HJLNP-UW-Z]{2})$/m';
$str = 'M1 1AA
M60 1NW
CR2 6XH
DN55 1PT
W1A 1HQ
EC1A 1BB
New ones:
M11AA
M1 1AA';
preg_match_all($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