JavaScript confirm msgbox delete records from MySQL database

Hi,

I have implemented a JavaScript function that should allow the user to confirm if they want to delete a record or not.  This is the code I have:

if(isset($_POST['delete'])) { ?>

<script type="text/javascript">
<!--
function confirmation() {
      var answer = confirm("Are you sure you want to delete?")
      if (answer){
            <?php
            mysql_query("DELETE FROM tblgbs WHERE gbID = $gbID") or die(mysql_error());
            mysql_query("DELETE FROM tblgb WHERE gbID = $gbID") or die(mysql_error());
            $success_msg = '<div class="errormsg">Deleted</div>';
            ?>
      }
      else{
            <?php
            $success_msg = '<div class="errormsg">Not Deleted</div>';
            ?>
      }
}
//-->
</script>

The problem is that the first time I enter the delete page, I do not get the confirm box, it just deletes the record.  The second problem I have is that even if I select Cancel, it still deletes the record.

I am using the following submit button to trigger the function:

<input class="subbtn" type="submit" name="delete" value="Delete" onclick="confirmation()" />


Please can someone have a look at this and tell me where I am going wrong.

Many thanks,

John