You will have $_GET['var'] and $_POST['var']. No problems.
$_GET and $_POST are arrays, so you will have no issues for them containing the same variable names.
However, if register_globals was ON (which is removed as of PHP 5.4), then you would look at the variables_order (EGPCS for example). In case it was EGPCS, then Post comes after Get, so the value of $var will be that of $_POST['var'].
You will have $_GET['var'] and $_POST['var']. No problems.
$_GET and $_POST are arrays, so you will have no issues for them containing the same variable names.
However, if register_globals was ON (which is removed as of PHP 5.4), then you would look at the variables_order (EGPCS for example). In case it was EGPCS, then Post comes after Get, so the value of $var will be that of $_POST['var'].
That's a good question, I would imagine it would depend on how the application handles global vars and in which order.