Object oriented style:
class XMLWriter {Procedural style:
bool xmlwriter_write_pi ( resource xmlwriter, string target, string content )Writes a processing instruction.
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
target
The target of the processing instruction.
content
The content of the processing instruction.