Object oriented style:
class XMLWriter {Procedural style:
bool xmlwriter_start_dtd ( resource xmlwriter, string qualifiedName [, string publicId [, string systemId]] )Starts a DTD.
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
qualifiedName
The qualified name of the document type to create.
publicId
The external subset public identifier.
systemId
The external subset system identifier.