[PHP] รบกวนช่วยทีนะคะ นำค่า ติกเลือก checkbox มาคำนวณแล้วแสดง จำนวนผลรวม sum ที่ได้ติกเลือก

Optional extra components :<br />
<input type="checkbox" name="optional1" id="optional1" value="Lithium-io battery" /> Lithium-io battery<br />
<imput type="hidden" name="price1" value="160">
<input type="checkbox" name="optional2" id="optional2" value="AC adaptor"/> AC adaptor<br />
<input type="hidden" name="price2" value="200">
<input type="checkbox" name="optional3" id="optional3" value="16GB class 4 SDHC memory card" /> 16GB class 4 SDHC memory card<br />
<input type="hidden" name="price3" value="250">
<input type="checkbox" name="optional4" id="optional4" value="8GB class 10 SDHC memory card" /> 8GB class 10 SDHC memory card
<input type="hidden" name="price4" value="310">
<input type="hidden" name="Line" value="4">

<?
$prices = 0;
  for($i=1; $i<($_POST["Line"]); $i++) 
  {
	if($_POST["optional$i"] != "")
	{
	    echo "<ul><li>";
		echo $_POST["optional$i"];
		$prices = $prices + $_POST["price$i"];
	    echo "</li></ul>";
	}
  }  

  echo "Total Cost $prices";
?>

Camera model:<br />
<input type="radio" name="model" value="Sirius" /> Sirius (10 megapixels; 4x optical zoom)
<input type="hidden" name="price1" value="160"><br />
<input type="radio" name="model" value="Arcturus" /> Arcturus (12 megapixels; 5x optical zoom)
<input type="hidden" name="price2" value="200"><br />
<input type="radio" name="model" value="Rigel"/> Rigel (14 megapixels; 5x optical zoom)
<input type="hidden" name="price3" value="250"><br />
<input type="radio" name="model" value="Antares"/> Antares (14 megapixels; 8x optical zoom)
<input type="hidden" name="price4" value="310">
<input type="hidden" name="Line" value="5"><br /><br />

Optional extra components :<br />
<input type="checkbox" name="optional1" id="optional1" value="Lithium-io battery" /> Lithium-io battery.
<input type="hidden" name="cost1" value="100"><br />
<input type="checkbox" name="optional2" id="optional2" value="AC adaptor"/> AC adaptor.
<input type="hidden" name="cost2" value="100"><br />
<input type="checkbox" name="optional3" id="optional3" value="16GB class 4 SDHC memory card" /> 16GB class 4 SDHC memory card.
<input type="hidden" name="cost3" value="100"><br />
<input type="checkbox" name="optional4" id="optional4" value="8GB class 10 SDHC memory card" /> 8GB class 10 SDHC memory card.
<input type="hidden" name="cost4" value="100">
<input type="hidden" name="Line" value="5">
<br /><br />
<input type="submit" value="Submit" name="submit" />
<input type="reset" value="Reset" name="reset" />

ลองเอาโค๊ดของท่านมาแปลงๆ ไม่รู้แบบเดียวกันไหม แต่ไม่ได้ผล

Camera model: ///////////////ส่วนของ radio
<? $prices = 0;
  for($i=1; $i<($_POST["Line"]); $i++) 
  {
	if($_POST["model$i"] != "")
	{
	    echo "<ul><li>";
		echo $_POST["model$i"];
		$prices = $prices + $_POST["price$i"];
	    echo "</li></ul>";
	}
  }  

  echo "Total Cost".'  '.'<b> $</b>'."<b>$prices</b>";?><br><br>

You selected the following extra components:<br>

<? /////////////////////// ส่วนของ checkbox
  $costs = 0;
  for($i=1; $i<($_POST["Line"]); $i++) 
  {
	if($_POST["optional$i"] != "")
	{
	    echo "<ul><li>";
		echo $_POST["optional$i"];
		$costs = $costs + $_POST["cost$i"];
	    echo "</li></ul>";
	}
  }  

  echo "Total Cost".'  '.'<b> $</b>'."<b>$cost</b>";