time math - calculate percentage of time

[gscharlemann]

I am having trouble computing the percentage of time spent doing an activity compared to the overall time.  I do:

$percent_time = ($time_swimming / $overall_time);
echo "$time_swimming / $overall_time<br>";
echo "percent swim = ".number_format($percent_time,4)."<br>";

I get the following:

 

00:17:22 / 01:33:45

percent swim = 0.0000

 

I'm stuck.

 

[corbin]

A computer has no concept of time.

 

 

00:17:22 does not mean 17 minutes and 22 seconds to a computer, it just means the string "00:17:22".

 

So what's happening is that PHP is casting the string to an int and the string is being casted to 0.

 

 

You'll need to do the math in seconds.  If you already have the time in seconds, then just use those variables instead.  If not, you can just use explode to separate the fields then multiply accordingly.

 

Then as far as the percentage math goes:

 

percent swimming = time swimming / total time * 100;

[gscharlemann]

10-4. Thanks Corbin. I'll give that a shot.

greg

[akitchin]

if you're grabbing this information from a database, you can use some of MySQL's native functions to help you out and unburden PHP a bit.