Object oriented style:
class XMLWriter {Procedural style:
bool xmlwriter_start_document ( resource xmlwriter [, string version [, string encoding [, string standalone]]] )Starts a document.
xmlwriter仅用于过程调用。resource 是被修改的 XMLWriter 资源。此资源来自对 xmlwriter_open_uri() 或 xmlwriter_open_memory() 的调用
versionThe version number of the document as part of the XML declaration. Defaults to 1.0.
encodingThe encoding of the document as part of the XML declaration. NULL by default.
standaloneyes or no. NULL by default.