So basically the addBodyClass method replaces some characters with - on the fly using regular expression:
public function addBodyClass($className)
{
$className = preg_replace('#[^a-z0-9]+#', '-', strtolower($className));
$this->setBodyClass($this->getBodyClass() . ' ' . $className);
return $this;
}
As you can see, when this method is called the original body classes are updated and the extra body class is added with a space between the original classes. So in order to add several classes I suggest you do the following in your xml file:
<action method="addBodyClass">
<className>classname1</className>
</action>
<action method="addBodyClass">
<className>classname2</className>
</action>
<action method="addBodyClass">
<className>classname3</className>
</action>
If you really want to be able to add several classes to the body using that method, then you will need to create a custom module that extends that method:
config.xml
<?xml version="1.0"?>
<config>
<modules>
<DigitalPianism_Multiplebodyclass>
<version>0.0.1</version>
</DigitalPianism_Multiplebodyclass>
</modules>
<global>
<blocks>
<page>
<rewrite>
<html>DigitalPianism_Multiplebodyclass_Block_Page_Html</html>
</rewrite>
</page>
</blocks>
</global>
</config>
Block/Page/Html.php
<?php
class DigitalPianism_Multiplebodyclass_Block_Page_Html extends Mage_Page_Block_Html
{
public function addBodyClass($classNames)
{
if (is_array($classNames))
{
foreach($classNames as $className)
{
parent::addBodyClass($className);
}
}
else parent::addBodyClass($classNames);
return $this;
}
}
Then in your custom helper you will be able to do:
public function addClasses() {
return array('classname1','classname2','classname3');
}