output_type: return data as either php native data types or xml encoded. ifphp is used, then the other values are ignored. default = xml
verbosity: determine compactness of generated xml. options are no_white_space, newlines_only, and pretty. default = pretty
escaping: determine how/whether to escape certain characters. 1 or more values are allowed. If multiple, they need to be specified as a sub-array. options are: cdata, non-ascii, non-print, and markup.default = non-ascii, non-print, markup
version: version of xml vocabulary to use. currently, three are supported: xmlrpc, soap 1.1, and simple. The keyWord auto is also recognized to mean respond in whichever version the request came in. default = auto (when applicable), xmlrpc
encoding: the encoding that the data is in. Since PHP defaults to iso-8859-1 you will usually want to use that. Change it if you know what you are doing. default=iso-8859-1