how to limit validate max 3 check box which are fetch from database (dynamic)

how to limit validate max 3 check box which are fetch from database (dynamic)

  <table width="140" border="0" cellspacing="0" cellpadding="0"> <tr>
                                          <td align="center" class="line"><input type="checkbox" name="ckb" value="<?php echo $relist['id']; ?>" onclick="chkcontrol(this.value)" />
                                            <span class="compare"><a href="#">Compare</a></span></td>
                                        </tr></table>

HTML:

 

Limiting check box is a Client side coding. So you need to execute JS to run it. And the problem with JS is anyone can control it via third party plugin.

I may not have understood your question

 

I just repeat my question
how to validate checkbox maximum select 3 checkbox when fourth checkbox is selected then show alert message

<?php 
								  $sqllist="select subitem.id, subitem.subitem, subitem.shortdesc, subitem.image, subitem.bid, subitem.sid, subitem.model, subitem.sales, subitem.salesdesc, subitem.description, brand.brand ".
                "from subitem, brand ".
                "where subitem.bid = brand.primid and pid=$pid and itemid=$itemid order by id asc";
								  
								  $pager = new PS_Pagination($conn, $sqllist, 10, 4, "pid=$pid&amp;itemid=$itemid");
								  $rslist = $pager->paginate();
								  $k=0;
								  while(@$relist=mysql_fetch_array($rslist))
								  {
								 
								  
								
								  
								   ?>
<input type="checkbox" name="ckb" value="<?php echo $relist['id']; ?>" onclick="chkcontrol(this.value)" />
<?php } ?>

PHP:

 

don't this validate? chkcontrol(this.value)

just check if the total value ==3 then alert and then set the value = 0 for the "this" check box.

So you must need to send "this" not only the "this.value" to restore the value

 

I trying javascript function but It's not working like this

<script type="text/javascript">
function chkcontrol(j) 
{
var total=0;

for(var i=0; i < document.brandform.["ckb[]"].length; i++)
{
if(document.brandform.ckb[i].checked)
{
total =total +1;
}
if(total > 3)
{
alert("Please Select Maximum 3 Product")
document.brandform.ckb[i].checked = false ;
return false;
}
}
} </script>

HTML:

<?php
                                  $sqllist="select subitem.id, subitem.subitem, subitem.shortdesc, subitem.image, subitem.bid, subitem.sid, subitem.model, subitem.sales, subitem.salesdesc, subitem.description, brand.brand ".
                "from subitem, brand ".
                "where subitem.bid = brand.primid and pid=$pid and itemid=$itemid order by id asc";
                                 
                                  $pager = new PS_Pagination($conn, $sqllist, 10, 4, "pid=$pid&amp;itemid=$itemid");
                                  $rslist = $pager->paginate();
                                  $k=0;
                                  while(@$relist=mysql_fetch_array($rslist))
                                  {
                                 
                                 
                               
                                 
                                   ?>
<input type="checkbox" name="ckb" value="<?php echo $relist['id']; ?>" onclick="chkcontrol(this.value)" />
<?php } ?>

PHP:

 

Try this out

<script type="text/javascript">
function chkcontrol(j)
{
var total=0;

for(var i=0; i < document.brandform.ckb.length; i++)
{
if(document.brandform.ckb[i].checked)
{
total =total +1;
}
if(total > 3)
{
alert("Please Select Maximum 3 Product")
document.brandform.ckb[i].checked = false ;
return false;
}
}
} </script>

Code (markup):

You just did a simple mistake