PHP how do I create this in PHP?

[Joveice]

So this site http://www.3dkingdoms.com/chess/elo.htm has this elo change calculator which is this

function CalculateRatingChange()

{

var Elo1 = document.rating.elo1.value * 1;

var Elo2 = document.rating.elo2.value * 1;

var K = document.rating.K.value * 1;

var EloDifference = Elo2 - Elo1;

var percentage = 1 / ( 1 + Math.pow( 10, EloDifference / 400 ) );

var win = Math.round( K * ( 1 - percentage ) );

var draw = Math.round( K * ( .5 - percentage ) );

if (win > 0 ) win = "+" + win;

if (draw > 0 ) draw = "+" + draw;

document.ratingchange.win.value = win;

document.ratingchange.draw.value = draw;

document.ratingchange.loss.value = Math.round( K * ( 0 - percentage ) );

document.ratingchange.percent.value =  Math.round( percentage * 100 ) + "%";

}

How can I create this in php? I don't need the form part of it, just the calulation part since it's gonna be used on the backend anyways, so just a simple php way to make this work where there is $elo1 $elo2 and $k

[dannytech357]

2 minutes ago, Joveice said:

So this site http://www.3dkingdoms.com/chess/elo.htm has this elo change calculator which is this

function CalculateRatingChange()

{

var Elo1 = document.rating.elo1.value * 1;

var Elo2 = document.rating.elo2.value * 1;

var K = document.rating.K.value * 1;

var EloDifference = Elo2 - Elo1;

var percentage = 1 / ( 1 + Math.pow( 10, EloDifference / 400 ) );

var win = Math.round( K * ( 1 - percentage ) );

var draw = Math.round( K * ( .5 - percentage ) );

if (win > 0 ) win = "+" + win;

if (draw > 0 ) draw = "+" + draw;

document.ratingchange.win.value = win;

document.ratingchange.draw.value = draw;

document.ratingchange.loss.value = Math.round( K * ( 0 - percentage ) );

document.ratingchange.percent.value =  Math.round( percentage * 100 ) + "%";

}

How can I create this in php? I don't need the form part of it, just the calulation part since it's gonna be used on the backend anyways, so just a simple php way to make this work where there is $elo1 $elo2 and $k

1. Change anything with var to $:

var Elo1 becomes $Elo1

2. Figure out what the values represent

document.rating.elo1.value probably would become $elo1

3. Change function names

Math.pow() becomes pow(), Math.round() becomes round()

4. Whenever referencing variables, make sure to prepend $

if (win > 0) becomes if ($win > 0)

 

That should be all that's really necessary, then echo it onto the page or whatever.

[Joveice]

1 minute ago, dannytech357 said:

1. Change anything with var to $:

var Elo1 becomes $Elo1

2. Figure out what the values represent

document.rating.elo1.value probably would become $elo1

3. Change function names

Math.pow() becomes pow(), Math.round() becomes round()

4. Whenever referencing variables, make sure to prepend $

if (win > 0) becomes if ($win > 0)

 

That should be all that's really necessary, then echo it onto the page or whatever.

Sounds straightforward, thanks.

[Joveice]

This is what I'v got so far 

<?php
$Elo1 = 2000;
$Elo2 = 2000;
$K = 32;
$EloDifference = $Elo2 - $Elo1;
$percentage = 1 / 1 + pow(10, $EloDifference / 400);
$win = round($K * 1 - $percentage);
$draw = round($K * .5 - $percentage);
if ($win > 0) {
$win = "+" + $win;
}if ($draw > 0) {
$draw = "+" + $draw;
}
echo $win;
echo '<br>';
echo $draw;
echo '<br>';
echo round($K * 0 - $percentage);
echo '<br>';
echo round($percentage * 100) + "%";



?>

Tho it returns the wrong values, when elo1 and elo2 is 2000 and K is 32 it should return win: +16 and draw = 0, and loss -16. this is not the case.

[mariushm]

php is case sensitive, make all variables lowercase so you won't get errors due to wrong variables.

use "."  to append two strings, not "+"  ...  not sure what you want with  $win = "+" + $win; and the other

add new lines after }  etc

 

$percentage = .. that line is wrong , you forgot the brackets .. ex 1 / (  1 +  ...  ) ;   as it is right now you have 1/1  +  ... which equals 1 + pow etc

brackets again for those round ( $K *  .5 +  )  .. round ($K * ( 0.5 +  ) )  ...   use 0.5 not .5

round ($k * 0 - $percentage )  ... will basically always do $k * 0 = 0  , so the result is round ( - $percentage)   ... the  ( ) are important, they establish order of computation just like with regular math.

 

 

 

[Joveice]

33 minutes ago, mariushm said:

php is case sensitive, make all variables lowercase so you won't get errors due to wrong variables.

use "."  to append two strings, not "+"  ...  not sure what you want with  $win = "+" + $win; and the other

add new lines after }  etc

 

$percentage = .. that line is wrong , you forgot the brackets .. ex 1 / (  1 +  ...  ) ;   as it is right now you have 1/1  +  ... which equals 1 + pow etc

brackets again for those round ( $K *  .5 +  )  .. round ($K * ( 0.5 +  ) )  ...   use 0.5 not .5

round ($k * 0 - $percentage )  ... will basically always do $k * 0 = 0  , so the result is round ( - $percentage)   ... the  ( ) are important, they establish order of computation just like with regular math.

 

 

 

I just tryed to copy the thing so not sure what most of it does

<?php
$elo1 = 2000;
$elo2 = 2000;
$k = 32;
$elodifference = ($elo2 - $elo1);
$percentage = ((1 / 1) + pow(10, ($elodifference / 400)));
$win = round($k * (1 - $percentage));
$draw = round($k * (0.5 - $percentage));
if ($win > 0) {
$win = "+".$win;
}if ($draw > 0) {
$draw = "+".$draw;
}
echo $win;
echo '<br>';
echo $draw;
echo '<br>';
echo round($k * (0 - $percentage));
echo '<br>';
echo round($percentage * 100)."%";



?>

This returns 

-32
-48
-64
200%

Which should be, +16, 0, -16, 50%

[vorticalbox]

why do server side? It isn't a function you need to keep private then you should move it client side to lower server load.

[mariushm]

Jesus dude, I say one thing and you do another...

Does it make sense to you to have  (1/1)  ? If you open calculator and enter there 1/1 what's the result?  Do you think the original formula wanted you to do a pointless division by 1 ?

 

anyway, here's what the php page should probably be .. including a basic form to play around with

 

<html>
<form name="rating" method="post" >
elo1 <input name="elo1" type="text" value="0" /> <br/>
elo2 <input name="elo2" type="text" value="0" /> <br/>
k <input name="k" type="text" value="32" /> <br/>
<input name="submit" type="submit" value="Calculate" /> 
<input name="submitted" type="hidden" value="1" />
</form>

<?php

if ($_POST['submitted']=='1') { // user pressed calculate and data was posted to server
// make sure what user posts is only 0..9 
if (ctype_digit($_POST['elo1']) == FALSE) die('elo1 is not an integer number');
if (ctype_digit($_POST['elo2']) == FALSE) die('elo2 is not an integer number');
if (ctype_digit($_POST['k']) == FALSE) die('k is not an integer number');

$elo1 = intval($_POST['elo1']); // convert the texts from the form to actual integer variables
$elo2 = intval($_POST['elo2']); 
$k = intval($_POST['k']);

$elo_diff = $elo2-$elo1;

$percentage = 1 / ( 1 + pow(10,($elo_diff / 400)));
$win = round($k * (1-$percentage));
$draw = round ($k * ( 0.5 - $percentage));
$loss = round ($k * ( 0 - $percentage));

$pvalue = round ($percentage * 100);

echo 'Win : ' . $win . '<br/>';
echo 'Draw: ' . $draw . '<br/>';
echo 'Loss: '. $loss . '<br/>';
echo 'Percentage: '. $pvalue .'% <br/>';

}

?>
</html>

 

[vorticalbox]

35 minutes ago, mariushm said:

Jesus dude, I say one thing and you do another...

Does it make sense to you to have  (1/1)  ? If you open calculator and enter there 1/1 what's the result?  Do you think the original formula wanted you to do a pointless division by 1 ?

 

anyway, here's what the php page should probably be .. including a basic form to play around with

 

<html>
<form name="rating" method="post" >
elo1 <input name="elo1" type="text" value="0" /> <br/>
elo2 <input name="elo2" type="text" value="0" /> <br/>
k <input name="k" type="text" value="32" /> <br/>
<input name="submit" type="submit" value="Calculate" /> 
<input name="submitted" type="hidden" value="1" />
</form>

<?php

if ($_POST['submitted']=='1') { // user pressed calculate and data was posted to server
// make sure what user posts is only 0..9 
if (ctype_digit($_POST['elo1']) == FALSE) die('elo1 is not an integer number');
if (ctype_digit($_POST['elo2']) == FALSE) die('elo2 is not an integer number');
if (ctype_digit($_POST['k']) == FALSE) die('k is not an integer number');

$elo1 = intval($_POST['elo1']); // convert the texts from the form to actual integer variables
$elo2 = intval($_POST['elo2']); 
$k = intval($_POST['k']);

$elo_diff = $elo2-$elo1;

$percentage = 1 / ( 1 + pow(10,($elo_diff / 400)));
$win = round($k * (1-$percentage));
$draw = round ($k * ( 0.5 - $percentage));
$loss = round ($k * ( 0 - $percentage));

$pvalue = round ($percentage * 100);

echo 'Win : ' . $win . '<br/>';
echo 'Draw: ' . $draw . '<br/>';
echo 'Loss: '. $loss . '<br/>';
echo 'Percentage: '. $pvalue .'% <br/>';

}

?>
</html>

 

You know you can just give the button a name and check if it posted, then you don't need the hidden input.

 

I still think a client side version is the way to go. You could even have sliders the change the output in real time.