$re = '/^(?:(?:S32\.(?:\w[25]|[1-35-8]\w)\w\w,?)+|(?:S32\.(?:\w[25]\w|4\w[1346-9])\w,?)+|(?:S32\.(?:\w[25]\w|4\w[235-9])\w,?)+|(?:S72\.(?:\w[14]\w|[0-8]\w[1346-9])\w,?)+|(?:S72\.(?:\w[14]\w|[0-8]\w[235-9])\w,?)+|(?:S72\.(?:[14]\w|9[1346-9])\w\w,?)+|(?:S72\.(?:[14]\w|9[235-9])\w\w,?)+)$/m';
$str = 'S72.91XB,S72.92XB
S72.211A
S72.414A,S72.415A
S32.509A
S32.301A,S32.821A
S32.421A,S32.422A
S32.421A
S32.421A,S32.509A';
preg_match_all($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