PHP Manual: Add variables to a WDDX packet with the specified ID

bool wddx_add_vars ( resource $packet_id , mixed $var_name [, mixed $... ] )

Serializes the passed variables and add the result to the given packet.

This function takes a variable number of parameters.

packet_id: A WDDX packet, returned by wddx_packet_start.
var_name: Can be either a string naming a variable or an array containing strings naming the variables or another array, etc.
...

Returns TRUE on success or FALSE on failure.