How to output a grouped list with multiple items selected in Joomla?

Question

In my .xml file I created the following grouped list:

<field name="mylistvalue" type="groupedlist" default="" label="Select an option" description="" multiple="true">
<group label="Color">
 <option value="red">red</option>
 <option value="blue">blue</option>
 <option value="green">green</option>
</group>
<group label="Size">
 <option value="small">small</option>
 <option value="medium">medium</option>
 <option value="large">large</option>
</group>
</field>

How can I output the selected values in my .php file?

For type="list" it works with:

<?php echo $params->get('mylistvalue');?>

For type="groupedlist" with the option multiple="true" I only get the output: Array and not the selected values.

Answer 1

How do you store these values? Seems that is an array and should be displayed as:

<?php foreach ($params->get('mylistvalue') as $value) : ?>
    <?php echo $value; ?>
<?php endforeach; ?>