php regular expression parse data - php

Question

I have a field which contain 20 character (pad string with space character from right) like below:
VINEYARD HAVEN MA
BOLIVAR TN
,
BOLIVAR, TN
NORTH TONAWANDA, NY
How can I use regular expression to parse and get data, the result I want will look like this:
[1] VINEYARD HAVEN [2] MA
[1] BOLIVAR [2] TN
[1] , or empty [2] , or empty
[1] BOLIVAR, or BOLIVAR [2] TN or ,TN
[1] NORTH TONAWANDA, or NORTH TONAWANDA [2] NY or ,NY
Currently I use this regex:
^(\D*)(?=[ ]\w{2}[ ]*)([ ]\w{2}[ ]*)
But it couldnot match the line:
,
Please help to adjust my regex so that I match all data above

Answer 1

What about this regex: ^(.*)[ ,](\w*)$ ? You can see working it here: http://regexr.com/3cno7.
Example usage:
<?php
$string = 'VINEYARD HAVEN MA
BOLIVAR TN
,
BOLIVAR, TN
NORTH TONAWANDA, NY';
$lines = array_map('trim', explode("\n", $string));
$pattern = '/^(.*)[ ,](\w*)$/';
foreach ($lines as $line) {
$res = preg_match($pattern, $line, $matched);
print 'first: "' . $matched[1] . '", second: "' . $matched[2] . '"' . PHP_EOL;
}

Answer 2

It's probably possible to implement this in a regular expression (try /(.*)\b([A-Z][A-Z])$/ ), however if you don't know how to write the regular expression you'll never be able to debug it. Yes, its worth finding out as a learning exercise, but since we're talking about PHP here (which does have a mechanism for storing compiled REs and isn't often used for bulk data operations) I would use something like the following if I needed to solve the problem quickly and in maintainable code:
$str=trim($str);
if (preg_match("/\b[A-Z][A-Z]$/i", $str, $match)) {
$state=$match[0];
$town=trim(substr($str,0,-2)), " ,\t\n\r\0\x0B");
}