I banged my head into the wall searching for this information.  I found it fragmented all over. I thought I should give back what I have learned in my quest for Actionscript to server communication by putting it in one spot.  So here it is Passing Actionscript to JavaScript to PHP to JavaScript to Actionscript without Flex, and without a daemon listening for sockets. 

     I have included for download the files I used to build this example.  It is listed as Example.rar.  You may see it functioning Here. Although I slapped it together and does not function well.  You might need to hit the button a couple times to get it going.  But it was built in only 2 hours so its bound to have some bugs.  The Variable passing is sound, its the loaders that need a bit of a tweek.

     In this example we will have a page that will pull a list of images from a MySQL database to display in a slide show.  To do this example you will need, Flash, a PHP editor, a JavaScript editor, and a MySQL database.  You will also need a decent knowledge of Actionscript, JavaScript, PHP, and MySQL.  I say decent because I am an animator that has learned to script.  You don't need to be a scripting god to do this.  So forgive the imperfections this will not be as elegant as it could be.

     We want the web page to display a series of images, but we don't want excessive load times, and we only want some of the images from the total gallery.  To accomplish this task we will place the images for the slide show in a folder and create a database to hold the picture name, locations, and type.  Then we will establish our lines of communication. 

     PHP is run on the server before the page loads.  After the page is loaded PHP is NOT active unless you have a daemon running in the background. Because of the nature of PHP, ExternalInterface.call can not directly call functions within it.  PHP writes its information from the server, then publishes it to the client as a normal HTML document.  To call functions in PHP with ExternalInterface.call you must go through JavaScript and a form.