No need for exit()
remove them all. There is no need to "end" the if else block. Once any condition is met, it ends.
$error_msg = "";
if(!isset($_POST["name"]) || empty($_POST["name"])) {
$error_msg="Not set name";
} else if(!isset($_POST["radio1"]) || empty($_POST["radio1"])) {
$error_msg="Not set question1";
} else if(!isset($_POST["radio2"]) || empty($_POST["radio2"])) {
$error_msg="Not set question2";
} else {
// Code to run if all post variables are set correctly.
}
if (!empty($error_msg)) {
// Display error message - echo $error_msg;
}