Update custom options magento in cart page

customoptions_update

use the onchange() function and pass parameters like this in default.phtml
Just place below code: 
 <?php if ($_options = $this->getOptionList()):
	$_customOptions = $_item->getProduct()->getOptions();
	if(!empty($_customOptions)){
	foreach ($_options as $_option) {
	$row['label'][]=$_option['label'];
	$myrow[$_option['label']][]=$_option['value'];
	}
	$optStr='';
	foreach($_customOptions as $optionKey =>$optionVal){
		$optStr.=  "<label class='required' style='width: 45%;'>".$optionVal->getDefaultTitle()."</label>";
$optStr.= "<select  style='width: 45%; min-width: 70px;' id='option_".$optionVal->getOptionId() .'_'.$_item->getId()."' onchange='updateproduct(".$_item->getId().",".$optionVal->getOptionId() .",this); 'name='options[".$optionVal->getOptionId() ."]'>";
 $optStr.=  "<option value=''>--Please Select--</option>";
 foreach($optionVal->getValues() as $valuesKey => $valuesVal) {
				$selected='';
					if(in_array($optionVal->getDefaultTitle(),$row['label']))
					{
if(in_array($valuesVal->getTitle(),$myrow[$optionVal->getDefaultTitle()]))
						$selected='selected';
					}
$optStr.= "<option value='".$valuesVal->getId()."' $selected >".$valuesVal->getTitle()."</option>";
                                }
$optStr.= "</select><br />";				
	}
echo($optStr);
	}else{
	?>
        <dl class="item-options">
            <?php foreach ($_options as $_option) : ?>
            <?php $_formatedOptionValue = $this->getFormatedOptionValue($_option) ?>
                <dt><?php echo $this->escapeHtml($_option['label']) ?></dt>
                <dd<?php if (isset($_formatedOptionValue['full_view'])): ?> class="truncated"<?php endif; ?>><?php echo $_formatedOptionValue['value'] ?>
                <?php if (isset($_formatedOptionValue['full_view'])): ?>
                <div class="truncated_full_value">
                    <dl class="item-options">
                        <dt><?php echo $this->escapeHtml($_option['label']) ?></dt>
                        <dd><?php echo $_formatedOptionValue['full_view'] ?></dd>
                    </dl>
                </div>
                <?php endif; ?>
            </dd>
            <?php endforeach; ?>
        </dl>
        <?php }
	endif;?>

Then in updateproduct script function, paste below code :

<script>
function updateproduct(itemid,optionid,obj)
{
var value=jQuery(obj).val();
/*var value= jQuery('#option_'+optionid+'_'+itemid+':option:selected').val();
alert(value);*/
postdate=$(obj).serialize()
//var postdata='{option['+optionid+']:' +value+'}';
jQuery.ajax({
	url :'<?php echo $this->getUrl('') ?>checkout/cart/myUpdate/id/'+itemid ,
	type: "POST",
	data: postdate,
	});
}
</script> 

Then in Checkout/controllers/CartController.php paste below function :
public function myUpdateAction()
	{
		$params = $this->getRequest()->getParams();
		
    $itemID = $params['id'];
    $item = Mage::getSingleton('checkout/session')->getQuote()->getItemById($itemID);
    
    $options =  $item->getOptions();
foreach ($params['options'] as $key=> $value) {
        $key=$key;
		$value=$value;
	 }
foreach ($options as $option) {
 $str= $option->getCode();
        if($str == 'option_'.$key)
        {
		    $option->setValue($value); 
        }
    }
$item->setOptions($options)->save(); 
Mage::getSingleton('checkout/cart')->save();
echo 'update';
	}
}

hello devjosh12

ajax response not working error return 404 status

code not working on page checkout/cart