well I found one solution that seemed to work.
in Flash I just set a variable to equal my toString()
flashVariable = formData.toString()
then in PHP, I just created another variable
$newVariable = $flashVariable
There might be more efficient andf better ways to approach this, but this was the only way I could come up with. Musicman, if you could post some code that you think might help my situation, that would be great. I'm still unsure about what you said about "The php script should contain a list of expected variables". How do you call those or pull those up??