How to multiply row from mysql by quantity from form? - php

Question

I've got the following code which now I would like to make to multiply $row['Price'] by quantity from form once the 'Buy' link has been clicked. I am a beginner so please don't judge, any help appreciated :) thanks
<table style="width:50%" id="table1" align="center">
<tr>
<th>Product Name</th>
<th>Price</th>
<th>Image</th>
<th>Quantity</th>
<th>Buy</th>
<?php
$query="SELECT * FROM products";
$result=mysqli_query($connection, $query);
while ($row=mysqli_fetch_assoc($result)){
echo "<tr>";
echo "<td>";
echo $row['ProductName'];
echo "</td>";
echo "<td>";
echo "$".$row['Price'];
echo "</td>";
echo "<td>";
echo ' <img src="./images/'.$row['Image'].'" style="width:50px;height:50px"/><br />';
echo "</td>";
echo "<td>";
echo "<form method='get' action='buy.php'>";
echo "<fieldset>";
echo "<input type='number' name='quantity' style='width:30px'/>";
echo "</td>";
echo "<td>";
echo 'Buy';
echo "</td>";
echo "</tr>";
echo "</fieldset>";
echo "</form>";
}

Answer 1

Short version:
You will need to post the quantity and the productID. than in your buy.php get the product price for that particular productID from the database and multiply that by the quantity. DO NOT POST THE PRICE IN YOUR FORM!!! please for the sake of programming do not post the product price in your form
Long version:
What you need:
1: A form (you have that already)
1b: A hidden form field that holds your product ID:
<input type='hidden' name="ProductID" value="<? echo $row['ProductID'];?>"/>
2: a submit button for your form:
<input type='submit' />
3: a page to recieve the form (you have that already: buy.php)
Now in your buy.php you can get the FORM variables like this:
echo $_POST['quantity'] ;
echo $_POST['ProductID'] ;
Now you need to get that product form the database to get the price
$query="SELECT * FROM products where ProductID=$_POST['ProductID']";
than multiply the price with the quantity
Do NOT send the price in the form... because people can edit that value!
thats why we send only the product ID and get the price from the database!!!!!
Also note that in this brief explanation i did not take form validation in consideration. But obviously you need to make sure that data you get from the is valid and not dangerous (google SQL injection to learn more)

Answer 2

for example your form is something like that
<form method='post' action='thispage.php'>
<input type="text" name="quantity" vlaue="1"> <!--you can get this value from form input no problem -->
</form>
<!-- now on thispage.php write the script you have posted on the question and on line Buy link you have to do something like that-->
<?php
#$q = $_POST['quantity'];
$value= $q*$row['Price'];
?>
echo 'Buy';
now you can get this value on page buy.php something like that
$value = $_GET['price'];
echo $value;