Object oriented style:
class XMLWriter {Procedural style:
bool xmlwriter_write_pi ( resource xmlwriter, string target, string content )Writes a processing instruction.
xmlwriter
Only for procedural calls. The XMLWriter resource that is being modified. This resource comes from a call to xmlwriter_open_uri() or xmlwriter_open_memory().
target
The target of the processing instruction.
content
The content of the processing instruction.