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

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 "<a href=".$_SERVER['PHP_SELF']."?mode=vote&voted=1&id=".$ratings[id].">Vote 1</a> | ";
Echo "<a href=".$_SERVER['PHP_SELF']."?mode=vote&voted=2&id=".$ratings[id].">Vote 2</a> | ";
Echo "<a href=".$_SERVER['PHP_SELF']."?mode=vote&voted=3&id=".$ratings[id].">Vote 3</a> | ";
Echo "<a href=".$_SERVER['PHP_SELF']."?mode=vote&voted=4&id=".$ratings[id].">Vote 4</a> | ";
Echo "<a href=".$_SERVER['PHP_SELF']."?mode=vote&voted=5&id=".$ratings[id].">Vote 5</a><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;
}

PS
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.