Newbie $HTTP_GET_VARS and $HTTP_POST_VARS confusion

I'm working my way through the *GET and *POST methods by looking at scripts that use these variables and have run up against some stuff that I can't seem to find documentation for. Specifically, I have an application that automatically generates html form processing scripts from selected MySQL tables and it's using some arguments I can't figure out. Could someone shed some light on the following snippets? $FormDict = $HTTP_GET_VARS; if ($HTTP_POST_VARS['fs0']) { $FormDict = $HTTP_POST_VARS; } I assume the above is determining which method (get or post) was used to submit the form data, but what I don't get is where the heck is the "fs0" in "$HTTP_POST_VARS" coming from. Is this a built in default variable in all posts? If so, It doesn't seem to be listed anywhere on the PHP site, any links to descriptions of built in fields in the get and post fields? $query .= buildCondition($FormDict['sf0'], $FormDict['so0'], $FormDict['ss0']); if ($FormDict['ss1']) { $query .= $FormDict['sc0'] . buildCondition($FormDict['sf1'], $FormDict['so1'], $FormDict['ss1']); } "buildCondition" is a class function auto generated by the MySQL form generator script I'm using, but again where is it getting the arguments 'sf0', 'so0', 'ss0'? More built-in fields? What are their human readable expansions of 'sf0', 'so0', 'ss0'? Thanks for any help, Ken