Description:
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According to http://www.w3.org/TR/REC-xml/#sec-pi a processing instruction should begin with <?something and end with ?>. But DOMDocument::createProcessingInstruction doesn't output the questionmark at the end.


Reproduce code:
---------------
<?php
$doc = new DOMDocument();
$pi = $doc->createProcessingInstruction('name', 'content');
$doc->appendChild($pi);
echo $doc->saveHTML();
?>


Expected result:
----------------
<?name content?>


Actual result:
--------------
<?name content>