(PHP 5 >= 5.1.2, PECL xmlwriter >= 0.1.0)
XMLWriter::writePI -- xmlwriter_write_pi — Writes a PI
面向对象风格
$target
   , string $content
   )过程化风格
$xmlwriter
   , string $target
   , string $content
   )Writes a processing instruction.
xmlwriter仅用于过程调用。被修改的 XMLWriter resource。此资源来自于对 xmlwriter_open_uri() 或 xmlwriter_open_memory() 的调用。
target
     The target of the processing instruction.
content
     The content of the processing instruction.
   成功时返回 TRUE, 或者在失败时返回 FALSE.