Since you can't load the text file 4 or 5 different times into all of the Movie Clips - It might be best if you changed the script around.
For example: In the PHP file you could change this part, $EcardText = "ToName=$ToName&..."
to something like $EcardText
That way the variable will be sent to the MC1 Movie clip instead of the main timeline. You would specify a Target in the Script instead of the Movie. All of them would have to be changed to the correct path to the text field located in the Movie Clip. Be sure to give all of the Movie Clips Instance Names, as you will be referencing them by that. If that makes sense.
I guess technically you can load the text file 4 or 5 different times to the different movie clips directly (Using the Target attribute of Loadvariables) but that may take longer for it to load. An example of this would be: