How to increase quantity and calculate total price and grand total in cart page.

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PHP

MySQL

I created cart detail page to user what product added in add to cart using cookies. I showed product image, name, price, quantity, total price and remove added product. If user increase quantiy of product, should total price automatacally calculate. If user decrease quantity should total price decrease. I set default quanity is 1.

Below is my code what i tryed.

What I have tried:

<?php
	$pro_id = $_COOKIE['product_id'];   
	$pro_id = explode(',', $pro_id);
	$qua = 1;
	foreach ($pro_id as $val) {
		$ans = "SELECT * FROM wm_products WHERE pro_id='$val'";
		$result = $conn->query($ans);
		while($row = $result->fetch_assoc()){
		?>
			<tr class="cart_item">
				<td>
					<a href="single-product.html"><img src="products_images/<?php echo $row['pro_img']; ?>" alt="" width="180" height="180"></a>
				</td>
				<td>
					<a href="single-product.html"><?php echo $row['pro_name']; ?></a>
				</td>
				<td>
					<span class="amount">Rs. <?php echo $row['pro_price']; ?></span>
				</td>
				<td>
					<div class="quantity buttons_added">
					<form action="" method="post">
						<input type="submit" class="minus" name="minus" value="-">				
						<input type="text" size="4" class="input-text qty text" title="Qty" value="<?php echo $qua;?>" name="" max="29" min="0" step="1" >
						<input type="submit" class="plus" name="plus" value="+">
					</form>					
					</div>
				</td>
				<td>
					<span class="amount">Rs. <?php echo number_format($row['pro_price'] * $qua); ?></span>
				</td>
				<td>
					<a class="remove remove_cart" href="#" dataid="<?php echo $row['pro_id']; ?>">×</a>
				</td>
			</tr>
		<?php 
		}                                   
	}
?>