PHP Manual: Writes a PI

Object-oriented style

public bool XMLWriter::writePi(string $target, string $content)

Procedural style

bool xmlwriter_write_pi(XMLWriter $writer, string $target, string $content)

Writes a processing instruction.

writer: Only for procedural calls. The XMLWriter instance that is being modified. This object is returned 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.

Returns true on success or false on failure.

Version	Description
8.0.0	`writer` expects an XMLWriter instance now; previously, a resource was expected.

XMLWriter::writePi