Passing a GET variable through a link with PHP

Hi there,

You haven't specified the $product_id variable on your page.php. Therefore, your conditional will always return false.

However what you can do instead is use a conditional to see if $_GET['id'] has been set, and if so return the product id into a variable. Here's how you'd do it:

<?php
if(isset($_GET['id'])){
  $product_id = $_GET['id'];
  echo $product_id;
} else {
  echo "failed";
}
?>

However there is a case where the product ID could actually be an empty string. So let's add another part to our conditional to check that the product ID is not an empty string.

<?php
if(isset($_GET['id']) && $_GET['id'] !== ''){
  $product_id = $_GET['id'];
  echo $product_id;
} else {
  echo "failed";
}
?>

Now, you can actually improve this code even further. Let's assume that you only want to return a page with the product ID if and only if the product ID entered is a valid number, and if it exists in the page. Else, just go to the main products page. You can do this with your header function like this:

<?php
// Check if the ID is set and the ID is NOT an integer
if(isset($_GET['id'] && !is_int($_GET['id'])){
  header('Location:pages.php');
  exit;
}

// Since the above code will cause the script to stop if this is true, 
// I no longer need an else statement. So continue the code as normal

$product_id = (isset($_GET['id']) ? $_GET['id'] : 0); 
// This is a ternary operator, something very powerful i think you should get to know :)
echo $product_id;
?>

This will mean that a product has to be specified with a number in order to assign the product id. If not, it will redirect the user to pages.php and assign the ID to 0.