Why can't I replace the movie clip in this example with another?

Question

http://www.sephiroth.it/tutorials/flashPHP/print_screen/page002.php

In this code, if I replace the movie clip with a different one, it does not work.
What am I doing wrong?

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Code:

function print_me(){
    video_mc.pause()    // first pause the playing video
    pn = new PrintScreen(); // initialize the PrintScreen class
    pn.addListener( listener ); // assign a listener
    pn.print(_root, 0, 0, 500, 210) // copy the _root
    loader.label = "computing... 0%"
    loader.open(true, true, true);  // open a loader
}

This calls the movie clip, but when I replace it with any other movie clip, it does not call the PHP.

listener.onComplete = function(target:MovieClip, load_var:LoadVars){
    loader.label = "sending to php..."
    load_var.send("files/pixels.php", "_blank", "POST")
    loader.close()
}

I feel something is missing or I am not able to understand correctly what the author is trying to explain.

Answer 1

video_mc.pause() this is a simple pause on your move clip

what your code is cause script alone from that page doesn't tell much about your problem