Description:
------------
PHP seems to ignore the encoding when parsing an UTF-8 encoded XML file, and assumes it is ISO-8859-1 instead.

The code below contains a very short XML file (inline) to parse, with the character a-with-tilde as value (this is just to show what happens, there is nothing special about this character). The a-with-tilde takes 2 bytes in UTF-8 encoding, and is represented as such in the XML file string.

The buggy behaviour is illustrated with the 3 possible PHP output encodings. Comment/uncomment the correct xml_parser_set_option() call to see the behaviour in all output encodings.

Note that nothing changes in behaviour if you change the encoding="utf-8" in the source XML into 'iso-8859-1', or remove it altogether, which shows that it is being ignored.

Reproduce code:
---------------
<?php

$xmlfile = "<?xml version=\"1.0\" encoding=\"utf-8\" ?><tag>\xC3\xA3</tag>";

function handler_data($parser, $data) {
  print "Data: $data\n";
  print "Length: ". strlen($data) ."\n";
}

$xml_parser = xml_parser_create();
xml_set_character_data_handler($xml_parser, "handler_data");
xml_parser_set_option($xml_parser, XML_OPTION_TARGET_ENCODING, "utf-8");
// xml_parser_set_option($xml_parser, XML_OPTION_TARGET_ENCODING, "iso-8859-1");
// xml_parser_set_option($xml_parser, XML_OPTION_TARGET_ENCODING, "us-ascii");

xml_parse($xml_parser, $xmlfile, 1);
xml_parser_free($xml_parser);

?>


Expected result:
----------------
With output encoding set to UTF-8, PHP should leave the data alone and should print 2 bytes (\xC3 and \xA3) for the a-with-tilde.

With output encoding set to ISO-8859-1, PHP should encode the a-with-tile as a single byte (\xE3).

With output encoding set to US-ASCII, PHP should output a single '?' to indicate the a-with-tilde is not available in the output encoding.

Actual result:
--------------
With output encoding set to UTF-8, PHP re-encodes the input into UTF-8, resulting in 4 bytes for a-with-tilde.

With output encoding set to ISO-8859-1, PHP leaves the input untouched.

With output encoding set to US-ASCII, PHP outputs two question marks.