<?php
function getCookie($key, $cookie) {
    if (preg_match('#' . preg_quote($key) . '=([\s\S]+?)(;|$)#i', $cookie, $output)) {
        return $output[1];
    }
}

$cookie = 'ct0=945d9ead4b3ce88d5aba8f09a4d78aee;foobar=945d9ead4b3ce88d5ab&a8f09a4d78aee';

var_dump(getCookie('ct0', $cookie));
var_dump(getCookie('foobar', $cookie));