PHP - นับจำนวน Row ของ Input โดยใช้ Session ครับ

<form name="item" method="post" action="test_echo2.php" ENCTYPE = "multipart/form-data" onsubmit="return checkform(this);">
    <div class="field" style=" font-weight: bold; " >
        Item ID<span class="mandatory">*</span><br>
        <a href="#" id="addScnt_item_id">Add Another Input Box</a>
        <div id="p_scents_item_id">
            <p>
            <label for="p_scnts_item_id"> <input type="text" id="item_id" size="20" name="item_id[]" style=" background-color: white; border: 1px solid #CCCCCC; padding: 8px; "/>         
 <input type="text" id="item_detail" size="20" name="item_detail[]" style=" background-color: white; border: 1px solid #CCCCCC; padding: 8px; "/> month       
            </label>
            </p>
        </div>
    </div>
    <div align="left">
        <input type="submit" class="ok_button" name="submit" value="ok" />
    </div>
</form>


<script type="text/javascript" src="http://code.jquery.com/jquery-1.4.3.min.js"></script>
<script>
$(function() {
        var scntDiv = $('#p_scents_item_id');
        var i = $('#p_scents_item_id p').size() + 1;
        
        $('#addScnt_item_id').live('click', function() {
            $('<p><label for="p_scnts_item_id"> <input type="text" id="item_id" size="20" name="item_id[]" style=" background-color: white; border: 1px solid #CCCCCC; padding: 8px; " /> <input type="text" id="item_detail" size="20" name="item_detail[]" style=" background-color: white; border: 1px solid #CCCCCC; padding: 8px; "/> month  <a href="#" id="remScnt">Remove</a></label></p>').appendTo(scntDiv);
                i++;
                return false;
        });
        
        $('#remScnt').live('click', function() { 
                if( i > 2 ) {
                        $(this).parents('p').remove();
                        i--;
                }
                return false;
        });
});
</script>

<?PHP
if(isset($_POST["submit"]))
    {

session_start();

	$_SESSION['item_id'] = $_POST['item_id'][$i];
	$_SESSION['item_detail'] = $_POST['item_detail'][$i];
    }
?>

<form name="Product_name" method="post" action="test_echo3.php" ENCTYPE = "multipart/form-data" onsubmit="return checkform(this);">
        <input type="submit" class="ok_button" name="submit2" value="ok" />
</form>

<?php
    if(isset($_POST["submit2"]))
    {
    echo count($_SESSION['item_id']);
    }
?>