Pass calculated value of SELECT box to php?

**deBassMan** · 08-10-2007, 07:11 PM

Hi all

here's what I need to achieve:

I have four select boxes on a form - all with values 0-100 (in increments of 10).

The total of all values must add up to 100.

E.g The first select box displays options 0-100 - let's say the user clicks 25.

the second select box should then display options - 0-75. Let's say the user clicks 15.

The third select box should offer options 0-60. This time the user clicks 60.

The fourth select box offers only 0.

The select boxes are being populated using a php loop.

I have tried to store the value of the first select box in a cookie using JScript and then read it back using php - it almost worked but seems to require a page refresh.

I considered storing the value in the registry instead of a cookie ...

then it hit me - AJAX!

All I really want to do is pass the value of each SELECT box and set the loop bounds for the next SELECT box accordingly.

Can anyone offer a simple way of implementing this?

thanks guys

**dsovic** · 08-27-2007, 10:16 AM

Take a look at this:

<html>
<head>
<style>
select {visibility:hidden}
</style>
<script language="JavaScript">
var maxValue = 100;
function start(){
// Be sure that first select is visible at startup
document.getElementById("select1").style.visibility = "visible";
}

function calculate(elemNo){
// generate current and next select's name
var currElemName = "select" + elemNo;
var nextElemName = "select" + (elemNo+1);
// and create corresponding objects
var currElem = document.getElementById(currElemName);
var nextElem = null;
// skip if there is no next element
try{
// try to create next element
var nextElem = document.getElementById(nextElemName);
// everithing is fine, initialize sum of selected options
var selValue = 0;
// perform summing
for(var i=0; i < elemNo; i++)
selValue += parseInt(document.getElementById("select"+(i+1)).options[document.getElementById("select"+(i+1)).selectedIndex].value);
// calculate max value for next element
maxValue = 100 - selValue;
// clear data,
while (nextElem.options.length > 1){
nextElem.options[0] = null;
}
// show it,
nextElem.style.visibility = "visible";
// and populate it
for(var i=0, optValue=0; optValue <= maxValue; i++, optValue += 10)
nextElem.options[i] = new Option(optValue, optValue);
// hide all others
for(var i=elemNo+1; i < 4; i++){
document.getElementById("select"+(i+1)).style.visibility="hidden";
}
}catch(e){
// elegant way to escape from javascript error

; simply do nothing
}
}
</script>
</head>
<body bgcolor="#FFFFFF" text="#000000" link="#804040" vlink="#008080" alink="#004080" onLoad="start();">
<form name="frm" method="POST">
<select name="select1" id="select1" onchange="calculate(1);">
<option value=0>0</option>
<option value=10>10</option>
<option value=20>20</option>
<option value=30>30</option>
<option value=40>40</option>
<option value=50>50</option>
<option value=60>60</option>
<option value=70>70</option>
<option value=80>80</option>
<option value=90>90</option>
<option value=100>100</option>
</select>
<select name="select2" id="select2" onchange="calculate(2);">
</select>
<select name="select3" id="select3" onchange="calculate(3);">
</select>
<select name="select4" id="select4" onchange="calculate(4);">
</select>
</form>
</body>
</html>

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