Once that you have your form posted, whether using POST or GET, you have all the information on one array. To use a variable that is within an array you will need to call the hole array and then specify which variable you need.
Suppouse that you have used the URL method, the code to 'print' a variable named 'x' will be
or, to make things easier, you can use the 'extract' function to brake the array into individual variables, see
and the same would be for the POST method, just replace the $_POST for the $_GET.