Represents nodes with character data. No nodes directly correspond to this class, but other nodes do inherit from it.
The contents of the node.
The length of the contents.
In case you're looking for the CDATA class to which nodes /do/ correspond, it's called DOMCdataSection (per my PHP installation) and isn't documented on php.net. Presumably, it doesn't add anything to this API.
See also: http://www.php.net/manual/en/domdocument.createcdatasection.php