PDO multiple select queries - php

Question

I am trying to get rows out of 2 tables. The first query works. But the second doesn't. This is my code:
echo '<table width="100%">';
echo '<tr><td>Product</td><td>Quantity</td><td>Price</td><td>Remove</td></tr>';
foreach ($_SESSION['cart'] as $key => $cartproduct) {
list($productid, $productquantity) = split("\|", $cartproduct, 2);
global $db;
$result = $db->prepare('SELECT name FROM products WHERE ID= :ID LIMIT 1; SELECT price FROM prices WHERE productid = :ID AND quantity = :quantity LIMIT 1');
$result->bindParam(':ID', $productid);
$result->bindParam(':quantity', $productquantity);
$result->execute();
$row = $result->fetch();
if($result->RowCount() == 1){
echo '<tr><td>' . $row['name'] . '</td><td>' . $productquantity . '</td><td>' . $row['price'] . '</td><td>Remove</td></tr>'; //LINE15
}else{
unset($_SESSION['cart'][$key]);
}
}
echo '</table>';
The row name is from the products table and the name price is from the prices table. This is the error I get:
Notice: Undefined index: price in /var/www/html/design2/pages/cart.php on line 15
I am sure the query is working. Can anyone tell my what i am doing wrong?

Answer 1

You are receiving index not defined because of the way your query is structured. You have:
SELECT name FROM products WHERE ID= :ID LIMIT 1; SELECT price FROM prices WHERE productid = :ID AND quantity = :quantity LIMIT 1
This is structured to return 2 result sets. You grab the first result set here:
$row = $result->fetch();
But then you try to access $row['price'] which doesn't exist in that result set. That result set is only the result from the first SELECT. You can see this if you just var_dump($row) and see what your result set looks like.
It looks like you can combine your query so that you get one result set:
SELECT p.name, pp.price FROM products p
INNER JOIN prices pp ON p.ID = pp.productid
WHERE p.ID= :ID AND pp.quantity = :quantity
LIMIT 1;
If you can't combine the queries into one, then you should iterate over your result sets and access the relevant $row index. That would look something like:
while($row = $result->fetch()) {
if(isset($row['name'])) {
//do something
} else if(isset($row['price'])) {
//do something else
}
}
Some things to consider:
You may need a LEFT JOIN instead of an INNER JOIN. This depends on
whether or not products always have a corresponding record in the
prices table.
I'm not sure what you're trying to achieve with
LIMIT 1. You may need to consider and ORDER BY -- unless it really
doesn't matter which record you return in your result.
You should consider testing your variables $productid and $productquantity to verify they have your intended values after splitting $cartproduct. What if one is empty / blank ?
You should test your result before trying to access the result array at a specific index.
For example:
if(isset($row['name']) && isset($row['price'])) {
//echo your results
} else {
//return an error
}