WP - Android Market QR Code

else if (strpos($url, "play.google.com/store") !== false) {

        // what to find in the string, in order to extract what we want
        $findthis = "?id=";
        // check where in the link "?id=" appears. we need the name of the app package.
        // to find the position of the start of the last occurence of a string, the idea is to reverse both $needle and $haystack, use strpos to
        // find the first occurence of $needle in $haystack, then count backwards by the length of $needle. finally, subtract $pos from length of $haystack.
        $packagepos = strlen($url) - (strpos(strrev($url), strrev($findthis)) + strlen($findthis));
        $packagename = substr($url,$packagepos+4); // extract the part of the link after "?id=" to the end of the string, that's the package name
        // check where/if the ampersand is that the web Market sometimes adds, so we can clean up the URL
        $ampersandpos = strpos($packagename, "&");
        // if the ampersand's position isn't bigger than 0, it doesn't exist, so ignore it
        if ($ampersandpos >0) {
            // extract the package name
            $packagename = substr($packagename, 0, $ampersandpos);
            // create a new Web Market URL, without the redundant info after the ampersand
            $url = substr($url, 0, strpos($url, "&"));
        }
        // create the Android Market search string for the QR code
        $qrURL = "market://search?q=pname:".$packagename;

    }