Php / Mysql While Loop Error - php

Question

Okay, none of those responses I used but I fixed it myself.
Im having trouble though trying to sum up all the prices for the books:
Code:
<style type="text/css">
table{font-size:1.11em;}
tr{background-color:#eee; border-top:1px solid #333;}
</style>
<?php
$con = mysql_connect("localhost","root","pass");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}
mysql_select_db("bookorama", $con);
$sql="SELECT customers.name, books.title, books.isbn, books.price
FROM customers, orders, order_items, books
WHERE customers.customerID = orders.customerID
AND orders.orderID = order_items.orderID
AND order_items.isbn = books.isbn;";
$result = mysql_query($sql); // You actually have to execute the $sql with mysql_query();
if($result === FALSE) {
die(mysql_error()); // TODO: better error handling
}
echo "<h1 style='color:#3366ff;'>Each customer book orders</h1>";
echo "<table>"; //start the table
while($row = mysql_fetch_array($result, MYSQL_ASSOC)) //Loop through the results
{
//echo each row of the table
echo "<tr>";
echo "<th><strong>Customer Name:</strong><br></th>";
echo "<td>$row[name]</td>";
echo "<th><strong>Book Title</strong><br></th>";
echo "<td>$row[title]</td>";
echo "<th><strong>ISBN</strong><br></th>";
echo "<td>$row[isbn]</td>";
echo "<th><strong>Book Price</strong><br></th>";
echo "<td>$row[price]</td>";
echo "</tr>";
}
echo '</table>'; //close out the table
?>

Answer 1

mysql_query returns FALSE on error, and you didn't check for this before trying to pass it to mysql_fetch_array.
You really should put error checking in your code!

Answer 2

Well maybe $result contains false because of error, add this block after mysql_query call.
if (!$result) {
die('Invalid query: ' . mysql_error());
}

Answer 3

Because your call $result = mysql_query($sql); has an error and returns false. You need to check for errors before you try to use a resource:
$result = mysql_query($sql);
if( !$result ) {
echo "SQL Query failed! " . mysql_error();
}
else {
// rest of your code here
}