If I'm understanding your problem, you need to pass the value of the type field into an action program. To do this, you can change your form definition to one of the following:
<form action="xyz.php3?type=a">
OR
<form action="xyz.php3">
<input type="hidden" name="type" value="a">
Using either method should work. Then in the action program, you can refer to $type to get the passed in value.