Processing Form Data /w $_POST

I have a form (setup.php) that passes values to processSetup.php when they are written into setup.txt. I'm trying to instead of writing every idividual value into setup.txt from setup.php, write a loop that will take as many values as there are in the $_POST array and write them all into a single array in logical order in setup.txt. I'm new to php and can't figure out how to do this. I'm thinking of something like... for ($_POST) { fwrite($setup, /*something to add current $_POST value to the end of an array within $setup*/); } How should I go about this? Thank you, -- Kyle