losing variables from javascript array when passing to php

Question

I'm trying to implement a page with a choice of user's preferences in an HTML form where if the checkbox ALL is selected then all sub-checkbox base1, base2 and base3 are checked automatically, and if any of sub-checkboxes is un-selected then the checkbox ALL must be unchecked. I used a javascript function which works but when I submit the form only the last variable in the array of checkboxes is sent.

<SCRIPT LANGUAGE="JavaScript">       
function checkChoice(field, i) {

if (i == 0) { // "All" checkbox selected.
if(field[0].checked==true) {
for (i = 1; i < field.length; i++)
field[i].checked = true;
   }
}
else  {  
if (field[i].checked == false) {
field[0].checked = false;
      }
   }
}

<form name="form" method = "POST" action="preferences.php">

<input type=checkbox name=classes1 value="allbases" onclick="checkChoice(document.form.classes1, 0)">All bases
</td><td>
<input type=checkbox name=classes1 value="base1" onclick="checkChoice(document.form.classes1, 1)">Base1
<br>
<input type=checkbox name=classes1 value="base2" onclick="checkChoice(document.form.classes1, 2)">Base2
<br>
<input type=checkbox name=classes1 value="base3" onclick="checkChoice(document.form.classes1, 3)">Base3
<input type="submit"  value="Set preferences" >

If I call the checkboxes'names in "classes1[]" all the values are submited but the javascript function doesn't work anymore. Is there a way of fixing this? Thanks for any help.

Community · Accepted Answer · 2017-05-23 10:33:13Z

0

For an alternative of checkChoice: check this SO question and the jsfiddle I presented there.

[edit] concerning your comment: a bit of extra thinking would have brought you to this solution

edited May 23, 2017 at 10:33

CommunityBot

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answered Apr 14, 2011 at 15:35

KooiInc

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5 Comments

Tornasole Over a year ago

Thanks, this could work if I had only one set of checkboxes in the form but I have six different sets like the one I posted so I cannot use getElementsbyTagName(input).

Tornasole Over a year ago

@Kooilnc Thank your for your help (I'm not at all familiar with javascript), in the end the combination works for me

function checkChoice(field, k) { if (field[k].checked == false) { field[0].checked = false;       } }  function flipCbs(obj) {  var cbs = document.getElementById('theForm').getElementsByTagName('input'),      l = cbs.length,      rangeid = obj.id.substr(0,2);   while (l--){   if (cbs[l].type.match(/checkbox/i)        && cbs[l] !== obj        && cbs[l].id.substr(0,2) === rangeid) {	       cbs[l].checked = obj.checked;    }  } }

Tornasole Over a year ago

@Kooilnc actually, the combination doesn't work as the POST array is always re-written but I'll keep trying.

Tornasole Over a year ago

@Kooilnc I used your function to create another I needed like this and it finally works!

function flip(obj) {  var commons = document.getElementById('theForm').getElementsByTagName('input'),      k = commons.length,      rangeid = obj.id.substr(0,2);   while (k--){   if (obj.checked==false&&commons[k].type.match(/checkbox/i)&&commons[k].id.substr(0,2) === rangeid&&commons[0].checked == true) {	       commons[0].checked = obj.checked;    }  } }

KooiInc Over a year ago

Hi Tomasole, glad I could contribute. Javascript is a nice & powerfull language once you get the hang of it. Happy coding!

james-geldart · Accepted Answer · 2011-04-14 15:33:19Z

0

All of the values actually ARE submitted but PHP will overwrite $_POST['classes1'] each time until you are just left with the last value. If however you add '[]' to your input names then they are added to an array.

Since the latter causes a problem with javascript, can you not just either a) iterate all of the form elements from the form.elements array, or b) give each input a unique id and use document.getElementById() to find it?

answered Apr 14, 2011 at 15:33

james-geldart

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