Retrieves the post category or categories from XMLRPC XML.

If the category element is not found, then the default post category will be
used. The return type then would be what $post_default_category. If the
category is found, then it will always be an array.

function xmlrpc_getpostcategory( $content ) {
	global $post_default_category;
	if ( preg_match( '/(.+?)/is', $content, $matchcat ) ) {
		$post_category = trim( $matchcat[1], ',' );
		$post_category = explode( ',', $post_category );
	} else {
		$post_category = $post_default_category;
	}
	return $post_category;
}