[thelist] strange php/mysql display problem

[Bob Meetin]

This seems really simple, yet causes heartache.

I am using a javascript program called flot to build charts and 
php/mysql to feed data.  Almost everything works but when I run a very 
very simple mather operation the chart fails. 

$query = "select count(rating) as num_ratings, sum(rating) as 
sum_ratings from some_table " ;
$result = mysql_query ($query);
$number_results = mysql_num_rows ($result);
if(mysql_num_rows($result)> 0)
{
   $row = mysql_fetch_array($result);
   $sum_ratings  = $row["sum_ratings"];  // the result here is "15"
   $num_ratings  = $row["num_ratings"]; // the result is "7"

   # $avg_rating = $sum_ratings / $num_ratings;  // this causes failure 
in the display
  
   $avg_rating = $sum_ratings / 7; // this works

   $avg_rating = number_format($avg_rating,1,".",",");
}

The failure is really peculiar. I have to comment out the mathematical 
equation for the chart to display, not just usage of $avg_rating, but 
then of course I lose automation in the calculations. For whatever 
reason the page does not like using $num_ratings as the denominator, but 
will allow the number 7.  They are equivalent.  

I tried some conversion which hasn't helped yet:

$num_ratings = intval(trim($num_ratings));

So, what is the problem with using the variable in the denominator?

-Bob