<html>
<head>Form</head>
<body>
	<script type="text/javascript">
		function odeme_degis(odeme){
			var odeme_url = "";

			switch(parseInt(odeme)){
				case 1:
				odeme_url = "kredikarti";
				break;

				case 2:
				odeme_url = "havale";
				break;

				case 3:
				odeme_url = "eft";
				break;

				case 4:
				odeme_url = "paypal";
				break;

				default:
				odeme_url = "";
				break;
			}

			if (odeme_url != ""){
				odeme_url = "?odeme_tipi=" +odeme_url;
			}

			document.odeme_form.action = 'submit.php'+odeme_url;
		}
	</script>
	
	<form method="post" action="submit.php" name="odeme_form" id="odeme_form">
		<input type="text" name="input1">
		<input type="text" name="input2">
		<select onchange="odeme_degis(this.value);">
			<option value="0">Ödeme Tipini Seçiniz</option>
			<option value="1">Kredi Kartı</option>
			<option value="2">Havale</option>
			<option value="3">EFT</option>
			<option value="4">Paypal</option>
		</select>

		<input type="submit" />
	</form>

</body>
</html>
http://pastebin.com/fkRvLhbB