$re = '/(?<= )[A-Za-z ]+(?=,? [A-Z]{2})/m';
$str = '6301 Stonewood Dr Apt-728, Plano TX-75024
13323 Maham Road, Apt # 1621, Dallas, TX 75240
17040 Carlson Drive, #1027 Parker, CO 80134
3465 25th St., San Francisco, CA 94110 ';
preg_match_all($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