Google PageRank PHP Class

It appears that Google has changed their Page Rank mechanism. I'm currently investigating ways to restore the functionality of this class.

Google PageRank Checker
While developers and designers can debate about the important of different search engine optimizations strategies, one metric that simply can't be argued is a website's Google PageRank, or its importance in driving traffic to the site.  Achieving a better PageRank was a consideration when redesigning this blog.  We can discuss how to achieve a better PageRank in another post -- this post will focus on how you can retrieve a page's Google PageRank using a small PHP class that I have created.

The base functions within this class were created by Jamie Scott -- all credit for the base functions go to him.  I've simply placed the functionality into PHP class format for easy use and updated the code to be a bit more transparent.  As far as PHP classes go, this one is quite small:

// Declare the class
class GooglePageRankChecker {

// Track the instance
private static $instance;

// Constructor
function getRank($page) {
// Create the instance, if one isn't created yet
if(!isset(self::$instance)) {
self::$instance = new self();
}
// Return the result
return self::$instance->check($page);
}


// Convert string to a number
function stringToNumber($string,$check,$magic) {
$int32 = 4294967296;  // 2^32
    $length = strlen($string);
    for ($i = 0; $i < $length; $i++) {
        $check *= $magic;
        //If the float is beyond the boundaries of integer (usually +/- 2.15e+9 = 2^31),
        //  the result of converting to integer is undefined
        //  refer to http://www.php.net/manual/en/language.types.integer.php
        if($check >= $int32) {
            $check = ($check - $int32 * (int) ($check / $int32));
            //if the check less than -2^31
            $check = ($check < -($int32 / 2)) ? ($check + $int32) : $check;
        }
        $check += ord($string{$i});
    }
    return $check;
}

// Create a url hash
function createHash($string) {
$check1 = $this->stringToNumber($string, 0x1505, 0x21);
    $check2 = $this->stringToNumber($string, 0, 0x1003F);

$factor = 4;
$halfFactor = $factor/2;

    $check1 >>= $halfFactor;
    $check1 = (($check1 >> $factor) & 0x3FFFFC0 ) | ($check1 & 0x3F);
    $check1 = (($check1 >> $factor) & 0x3FFC00 ) | ($check1 & 0x3FF);
    $check1 = (($check1 >> $factor) & 0x3C000 ) | ($check1 & 0x3FFF);

    $calc1 = (((($check1 & 0x3C0) << $factor) | ($check1 & 0x3C)) << $halfFactor ) | ($check2 & 0xF0F );
    $calc2 = (((($check1 & 0xFFFFC000) << $factor) | ($check1 & 0x3C00)) << 0xA) | ($check2 & 0xF0F0000 );

    return ($calc1 | $calc2);
}

// Create checksum for hash
function checkHash($hashNumber)
{
    $check = 0;
$flag = 0;

$hashString = sprintf('%u', $hashNumber) ;
$length = strlen($hashString);

for ($i = $length - 1;  $i >= 0;  $i --) {
$r = $hashString{$i};
if(1 === ($flag % 2)) {  
$r += $r;
$r = (int)($r / 10) + ($r % 10);
}
$check += $r;
$flag ++;
}

$check %= 10;
if(0 !== $check) {
$check = 10 - $check;
if(1 === ($flag % 2) ) {
if(1 === ($check % 2)) {
$check += 9;
}
$check >>= 1;
}
}

return '7'.$check.$hashString;
}

function check($page) {

// Open a socket to the toolbarqueries address, used by Google Toolbar
$socket = fsockopen("toolbarqueries.google.com", 80, $errno, $errstr, 30);

// If a connection can be established
if($socket) {
// Prep socket headers
$out = "GET /search?client=navclient-auto&ch=".$this->checkHash($this->createHash($page))."&features=Rank&q=info:".$page."&num=100&filter=0 HTTP/1.1\r\n";
$out .= "Host: toolbarqueries.google.com\r\n";
$out .= "User-Agent: Mozilla/4.0 (compatible; GoogleToolbar 2.0.114-big; Windows XP 5.1)\r\n";
$out .= "Connection: Close\r\n\r\n";

// Write settings to the socket
fwrite($socket, $out);

// When a response is received...
$result = "";
while(!feof($socket)) {
$data = fgets($socket, 128);
$pos = strpos($data, "Rank_");
if($pos !== false){
$pagerank = substr($data, $pos + 9);
$result += $pagerank;
}
}
// Close the connection
fclose($socket);

// Return the rank!
return $result;
}
}
}
The createHash and checkHash methods perform the deep down mathematical operations.  Once those are out of the way, the check method connects to Google's toolbar server, disguising itself as a toolbar via the User-Agent header, to get the page's PageRank.  A singleton pattern is used since creating individual instances isn't important:

$rank = GooglePageRankChecker::getRank("davidwalsh.name"); // returns "5"
The number provided back represents the PageRank for the URL provided!  This PHP class can be used on its own, but I've created a MooTools-powered script to retrieve an address' PageRank via some simple AJAX.