Sending image data from Flash to PHP. Help!

[Jazztronik]

I want to allow the user of a flash movie to display on the browser (or to force download) an image within a Sprite, as a JPG image/file.

I started from a pre-made class located on sephiroth.it:
http://www.sephiroth.it/tutorials/fl.../print_screen/

but as this code was made in AS2, I decided to create my own AS3 class based on this one, and the result I get on the browser is a one pixel column of 1x300 pixels (the sprite size is 300x300). For some reason, the data passed from Flash to PHP is not processed right.

This is the code I made:

JPGExporter class (JPGExporter.as):

package {
    
    import flash.display.BitmapData;
    import flash.geom.Rectangle;
    import flash.geom.ColorTransform;
    import flash.geom.Matrix;
    import flash.utils.Timer;
    import flash.events.TimerEvent;
    import EventImgProcess;    // custom event class for events of image processing
    import flash.events.EventDispatcher;
    import flash.display.DisplayObject;
    import flash.net.URLVariables;
    
    public class JPGExporter extends EventDispatcher {
        
        private var timer:Timer = new Timer(5);
        public var record:URLVariables; // used to stored all the data to send
        private var _container:DisplayObject;
        private var bmp:BitmapData;
        
        public function JPGExporter(container:DisplayObject, x:Number, y:Number, w:Number, h:Number) {
            _container = container as DisplayObject;
                        
            bmp = new BitmapData(w, h, false);
            record = new URLVariables();
            record.width = w;
            record.height = h;
            record.col = 0;
            record.row = 0;
            
            var matrix:Matrix = new Matrix();
            matrix.translate(-x, -y);
            
            bmp.draw(container, matrix, new ColorTransform(), null, new Rectangle(0, 0, w, h));
            
            timer.addEventListener(TimerEvent.TIMER, copySource);
            timer.start();
        }
        
        private function copySource(e:TimerEvent):void {
            var pixel:Number;
            var str_pixel:String;
            record["px" + record.row] = new Array();
            // Get row specified by row property of record (URLVariables)
            for (var a:uint = 0; a < bmp.width; a++) {
                pixel = bmp.getPixel(a, record.row);
                str_pixel = pixel.toString(16);
                if (pixel == 0xFFFFFF) str_pixel = ""; // don't send blank pixels
                record["px" + record.row].push(str_pixel);
            }
            
            record.row += 1;
            
            if (record.row >= bmp.height) {
                timer.stop();
                                // trigger the complete event and pass through it the processed data in order to send it
                dispatchEvent(new EventImgProcess(EventImgProcess.IMAGE_COMPLETE, record));
                bmp.dispose();
            }
        }
        
    }    
    
} 

Code in the FLA file (test.fla):

imageProcess = new JPGExporter(mySprite, 0, 0, mySprite.width, mySprite.height);
    
imageProcess.addEventListener(EventImgProcess.IMAGE_COMPLETE, onImageComplete);

function onImageComplete(e:EventImgProcess):void {
    var variables:URLVariables = e.variables as URLVariables; // I get the URLVariables instance containing all the data through my custom event
    var request:URLRequest = new URLRequest("http://localhost/.../pixels2JPG.php");
    request.method = URLRequestMethod.POST;
    request.contentType = "application/x-www-form-urlencoded";
    request.data = variables;
    trace("Image processing complete");
    navigateToURL(request, "_blank");    
} 

And the PHP (pixels2JPG.php):

<?php

error_reporting(0);
/**
 * Get the width and height of the destination image
 * from the POST variables and convert them into
 * integer values
 */
$w = (int)$_POST['width'];
$h = (int)$_POST['height'];

// create the image with desired width and height

$img = imagecreatetruecolor($w, $h);

// now fill the image with blank color
// do you remember i wont pass the 0xFFFFFF pixels 
// from flash?
imagefill($img, 0, 0, 0xFFFFFF);

$rows = 0;
$cols = 0;

// now process every POST variable which
// contains a pixel color
for($rows = 0; $rows < $h; $rows++){
    // convert the string into an array of n elements
    $c_row = explode(",", $_POST['px' . $rows]);
    for($cols = 0; $cols < $w; $cols++){
        // get the single pixel color value
        $value = $c_row[$cols];
        // if value is not empty (empty values are the blank pixels)
        if($value != ""){
            // get the hexadecimal string (must be 6 chars length)
            // so add the missing chars if needed
            $hex = $value;
            while(strlen($hex) < 6){
                $hex = "0" . $hex;
            }
            // convert value from HEX to RGB
            $r = hexdec(substr($hex, 0, 2));
            $g = hexdec(substr($hex, 2, 2));
            $b = hexdec(substr($hex, 4, 2));
            // allocate the new color
            // N.B. teorically if a color was already allocated 
            // we dont need to allocate another time
            // but this is only an example
            $test = imagecolorallocate($img, $r, $g, $b);
            // and paste that color into the image
            // at the correct position
            imagesetpixel($img, $cols, $rows, $test);
        }
    }
}

// print out the correct header to the browser
header("Content-type:image/jpeg");
// display the image
imagejpeg($img, "", 90);
?>

What do you think is going wrong?