Inaccurate calculations (rounding?) - PHP

Question

Edit: Problem solved

I'm trying to port over a popular rating algorithm which analyses some statistics from Counter-Strike matches into a PHP script. The outline of the system can be found in the link below (the bottom part of the news post): http://www.hltv.org/?pageid=242&eventid=0

Anyway, so I've get everything set up in PHP, and I'm reasonably sure that everything is correct. For the purposes of calcuation, assume that:

$rating1K = 5;
$rating2K = 8;
$rating3K = 3;
$rating4K = 0;
$rating5K = 0;
$kills = 30
$deaths = 19
$round = 30

This is my code:

$kpr = $kills / $round; // kills per round
$killRating = ($kills / $round / $kpr); 

$spr = ($round - $deaths) / $round; // survivals per round
$survivalRating = ($round - $deaths) / $round / $spr;    

$averageRMK = ((1*$rating1K + 4*$rating2K + 9*$rating3K + 16*$rating4K + 25*$rating5K)/$round);
$roundsWithMultipleKillsRating = ((1*$rating1K + 4*$rating2K + 9*$rating3K + 16*$rating4K + 25*$rating5K)/$round/$averageRMK);

$rating = ($killRating + 0.7 * $survivalRating + $roundsWithMultipleKillsRating) / 2.7;
echo $rating; 

The problem is that $killRating, $survivalRating and $roundsWithMultipleKillsRating always seem to return 1 in the PHP script, whereas if I calculate them manually myself they are different. For example, if I calculate $killRating myself, I get 1.5789-etc, but PHP returns "1".

What can I do this fix this problem?

Thanks a lot.

Answer 1

You are calculating wrong...

$kpr = $kills / $round; // kills per round
$killRating = ($kills / $round / $kpr); 

equals

$kpr = 30 / 30; // 1
$killRating = (30 / 30 / 1); //1

And

$spr = ($round - $deaths) / $round; // survivals per round
$survivalRating = ($round - $deaths) / $round / $spr;

equals

$spr = (30 - 19) / 30; // 0.36666
$survivalRating = (30 - 19) / 30 / 0.3666; // 1

Your own calculation is wrong. PHP does everything fine here.

Please note that kpr being $kill/$round, when you devide $kill/$round/$kpr it will always be 1. Any number divided by itself equals 1. I can't beleive everyone is talking about floats and integers without even understanding mathematics...

Answer 2

$kills = 30;
$deaths = 19;
$round = 30;

$kpr = $kills / $round; // kills per round
$killRating = ($kills / $round / $kpr);

For KPR: kills / round = 30 / 30 = 1

For KillRating: kills / round / kpr = 30 / 30 / 1 = 1 (this is just kpr/kpr, why?)

PHP is giving you 1 as the answer to that part because the answer is 1.

Answer 3

Ensure you are dealing with floats instead of integers. Try casting them.