(PHP 5, PHP 7)
DOMDocument::createProcessingInstruction — Creates new PI node
$target
   [, string $data
  ] )This function creates a new instance of class DOMProcessingInstruction. 此节点出现在文档中,除非是用诸如 DOMNode->appendChild() 等函数来将其插入。
targetThe target of the processing instruction.
dataThe content of the processing instruction.
   The new DOMProcessingInstruction or FALSE if an error occurred.
  
DOM_INVALID_CHARACTER_ERR
       Raised if target contains an invalid character.