please help me how to add coding to count the quantity of product if user wan to buy the product more than 1..
Below is my php coding

PHP Code:
<?php
require_once( "dblib.php" );
session_start();
$products get_products();
$categories get_categories();

if(isset (
$_SESSION['username']))
    
$username $_SESSION['username'];
else
    
$username 'Guest';
?>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>Baby's Store</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<style type="text/css">
<!--
.style1 {
    color: #FFFFFF;
    font-weight: bold;
}
.style9 {color: #660000; font-weight: bold; }
-->
</style>
</head>
<script>
function buy( prod_id, cat_id )
{
    document.getElementById( 'prod_id' ).value = prod_id;
    document.getElementById( 'cat_id' ).value = cat_id;
    document.getElementById( 'buyform' ).submit();
    return null;
}
</script>
<body>
<form id="buyform" action="add.php" method="post">
<input type="hidden" name="prod_id" id="prod_id" value="" />
<input type="hidden" name="cat_id" id="cat_id" value="" />
</form>
<table width="1145" height="400" border="2" align="center" bordercolor="#330033" bgcolor="#FF9999">
  <tr>
      <!-- banner -->
    <td height="44" colspan="2" valign="top"><img src="banner.jpg" width="1133" height="60"></td>
  </tr>
  <tr>
      <!-- menu 1 -->
    <td height="23" colspan="2" valign="top"><div align="center" class="style1">:: <a href="index2.php?home">HOME</a> ::  <a href="index2.php?help">HELP</a> :: FAQ :: 
    <?php
    
if($username=='Guest'
    {    echo 
'<a href="index2.php?login">LOGIN</a>'; }
    else 
    {    echo 
'<a href="index2.php?logout">LOGOUT</a>'; }
    
?>
    
     :: <a href="index2.php?register">REGISTER</a> ::</div></td>
  </tr>
  <tr>
      <!-- menu 2 left column -->
    <td width="214" valign="top"><br>
    <p><b>Welcome <?php echo ($username?></b></p>       
      
      <strong>Baby's Categories</strong><strong>
      <!--This is menu section-->
      </strong>
      <ul>
        <?php foreach ($categories as $category
        { 
?>
        <li><a href="index2.php?catid=<?php echo( $category['cat_id'] ); ?>" title="Display products of this category"><?php echo( $category['name'] ); ?></a></li>
        <?php 
        
?>
        <p>&nbsp;</p>
    </ul>    </td>
    <!-- body right column -->
    <td width="913" align="left" valign="top" bordercolor="#FFFFFF"><p><br>
        <!-- table dlm body -->    
      <table width="903" height="120" border="0">
        <tr>
          <td>
          <table width="908" height="93" border="0" align="center">
            <tr>
              <td width="563">
                <!--catalog-->
                <?php            
                
if (isset($_GET['help']))
                {    include 
'help.php';  }
                
                else if (isset(
$_GET['logout']))
                {    include 
'logout.php';  }
                
                
//else if (isset($_GET['forgot']))
                //{    include 'forgot.php';  }
                
                
else if (isset($_GET['checkout']))
                {    include 
'checkout.php';  }
                
                else if (isset(
$_GET['register']))
                {    
                    if (
$_GET['login'] == 'success')
                    {    echo 
'Your form is submitted'; }
                    else if(
$_GET['login'] == 'failed')
                    {    echo 
'Please fill all the field in the form'; }
                    include 
'registerform.php'
                }
          
                else if (isset(
$_GET['catid']))
                {
                    
$catid $_GET['catid'];
                    
$products get_product_by_category($catid);
                
?>
                    <table width="100%">
                        <strong>PRODUCTS</strong>
                          <!--This is content section-->
                          <p></p>
                          <?php foreach( $products as $product 
                        { 
?>
                          <tr>
                        <td width="40%"><?php echo( $product['p_name'] ); ?></td>
                        <td width="15%" align="center"><img src=product_image/<?php echo $product['p_id'?>.jpg></td>
                        <td width="15%" align="right">$<?php echo( $product['p_price'] ); ?></td>
                        <td width="30%" align="center"><a href="javascript:buy( <?php echo( $product['p_id'] ); ?>,
                            <?php echo( $catid ) ; ?> );">add to cart</a></td>
                        </tr>
                          <?php                        
                          
?>
                    </table>
                  </td>
                  <td width="335" valign="top"><strong>SHOPPING CART</strong>
                      <!--shopping cart-->
                      <?php
                        
if( isset( $_SESSION['cart'] ) ) 
                        {
                        
?>
                            <!-- CART : <?php echo( join","array_keys$_SESSION['cart'] ) ) ); ?> -->
                            <table width="97%" height="65" cellpadding="5" cellspacing="0">
                            <tr>
                                <td><u>Product</u></td>
                                <td><u>Price</u></td>
                                <td><u>Qty</u></td>
                            </tr>
                            <?php
                            $qty 
0$i=0;    
                            foreach( 
array_keys$_SESSION['cart'] ) as $product 
                            {                    
                                
$info product_info$product );
                            
?>                      
                            <tr>
                                  <td width="52%"><?php echo( $info['p_name'] ); ?></td>
                                <td width="25%"><?php echo( $info['p_price'] ); ?>
                                      <div align="center"></div></td>
                                     <?php $total += $info['p_price']?>
                                <td width="23%"><?php if ($info['p_id']==$info['p_id'])
                                    
$qty++; echo $qty;?>   
                                </td>
                            </tr>
                               <?php 
                            
//$i++;
                            
}?>
                            <tr>
                                <td><hr><strong>Total</strong></td>
                                <td><hr><strong><?php  echo $total?></strong></td>
                                <td><hr><strong>
                                    <?php $t_qty += $qty;
                                    echo 
$t_qty?>    </strong>
                                </td>
                            </tr>
                            <tr>
                                  <td colspan="3" align="center"><a href="index2.php?checkout">Checkout</a></td>
                            </tr>                        
                                 </table>
                </td>
                          <?php
                          
}                         
                }
                else if (isset(
$_GET['login']))
                {    include 
'loginform.php'; }
                  
                else if (isset(
$_GET['bad']))
                {    
                    echo 
'Bad login or password, please try again'
                    include 
'loginform.php';                                            
                }
                else 
                {    include 
'home.php';  }?>
            </tr>
          </table>
          </td>
        </tr>
    </table></td>
  </tr>
  <tr>
    <td colspan="2" valign="top"><div align="center" class="style9">Copyright &copy; 2009 babyonline.com </div></td>
  </tr>
</table>

</body>
</html>