Detect main colors in an image with PHP

I am trying to replicate the functionality that Dribbble.com does with detecting the predominant colors in an Image. In the image below you can see a screenshot from Dribbble.com that shows the 8 predominant colors in the image to the left. Here is the actual page in the image http://dribbble.com/shots/528033-Fresh-Easy?list=following

I need to be able to do this in PHP, once I get the colors I need I will save them to a database so the processing does not need to be run on every page load.

After some research on how to get these colors out of an Image, some people said you simply examine an image pixel by pixel and then save the colors that occur the most. Other say there is more to it and that getting the colors that exist the most frequent won't give the desired affect. They say you need to Quantize the image/colors (I am lost at this point).

In the image below the Dribble shot below is a Javascript library that does the same thing, that page can be viewed here http://lokeshdhakar.com/projects/color-thief/

Viewing the source of that page I can see there is a Javascript file named quantize.js and the results are really good. So I am hoping to be able to do what that Javascript library does but with PHP and GD/ImageMagick

I had found this function that will return the colors and count in an Image with PHP but the results are different from the Javascript version above and the Dribble results

/**
 * Returns the colors of the image in an array, ordered in descending order, where the keys are the colors, and the values are the count of the color.
 *
 * @return array
 */
function Get_Color()
{
    if (isset($this->image))
    {
        $PREVIEW_WIDTH    = 150;  //WE