PHP/MySQL - Need help in correcting a PHP warning? - php

Question

I found this script on about.com which I'm trying to learn from on how to create a rating system but the script gives me a warning that I listed below.
I was wondering how can I fix this problem? And what part of the code do I need to change and where?
Here is the warning below.
Warning: Division by zero on line 43
Here is the script below.
<?php
// Connects to your Database
mysql_connect("localhost", "root", "", "sitename") or die(mysql_error());
mysql_select_db("sitename") or die(mysql_error());
//We only run this code if the user has just clicked a voting link
if ( $mode=="vote")
{
//If the user has already voted on the particular thing, we do not allow them to vote again $cookie = "Mysite$id";
if(isset($_COOKIE[$cookie]))
{
Echo "Sorry You have already ranked that site <p>";
}
//Otherwise, we set a cooking telling us they have now voted
else
{
$month = 2592000 + time();
setcookie(Mysite.$id, Voted, $month);
//Then we update the voting information by adding 1 to the total votes and adding their vote (1,2,3,etc) to the total rating
mysql_query ("UPDATE vote SET total = total+$voted, votes = votes+1 WHERE id = $id");
Echo "Your vote has been cast <p>";
}
}
//Puts SQL Data into an array
$data = mysql_query("SELECT * FROM vote") or die(mysql_error());
//Now we loop through all the data
while($ratings = mysql_fetch_array( $data ))
{
//This outputs the sites name
Echo "Name: " .$ratings['name']."<br>";
//This calculates the sites ranking and then outputs it - rounded to 1 decimal
$current = $ratings[total] / $ratings[votes];
Echo "Current Rating: " . round($current, 1) . "<br>";
//This creates 5 links to vote a 1, 2, 3, 4, or 5 rating for each particular item
Echo "Rank Me: ";
Echo "Vote 1 | ";
Echo "Vote 2 | ";
Echo "Vote 3 | ";
Echo "Vote 4 | ";
Echo "Vote 5<p>";
}
?>

Answer 1

You need to make sure you aren't dividing using a 0. If the values you get for total and votes from MySQL are 0, you should bypass the division and set a fixed value.
//This calculates the sites ranking and then outputs it - rounded to 1 decimal
if($ratings['total'] > 0 && $ratings['votes'] > 0) {
$current = $ratings['total'] / $ratings['votes'];
}
else{
$current = 0;
}
P.S.
Note how I quoted the elements in the $ratings array. You should always do that.
// This is INCORRECT. Causes error notices if you have error reporting on.
// and can have other consequences if you happen to use a `total` constant.
$ratings[total];
// It should be
$ratings['total']

Answer 2

The problem is here
$current = $ratings[total] / $ratings[votes];
If there are no votes, you are dividing a number by zero. And that is bad :)
Add some verification that $ratings[votes] is set and it is not 0.