Description:
------------
I got warning/error using dump_mem(true,'ISO-8859-1') and accentuation 

put a '?/?/?/?' or any accent char and press 'go'

that crash converter


$xmlDoc->dump_mem(true, 'ISO-8859-1');


Reproduce code:
---------------
<?
if (!isset ($submit)) { ?>
<form action="<?php echo $SCRIPT_NAME ?>" method="POST">
champ1 : <input type="text" name="txt1" /><br/>
champ2 : <input type="text" name="txt2" /><br/>
champ3 : <input type="text" name="txt3" /><br/>
<input type="submit" name="submit" value="go" /><br/>
</form>
<?
} else {
	$xmlDoc = domxml_new_doc('1.0');
	$root = $xmlDoc->add_root("root");
	while(list($key, $value) = each($HTTP_POST_VARS)) {
		$nodeName = $root->new_child($key, $value);
	};
	echo $xmlDoc->dump_mem(true, 'ISO-8859-1');
};
?>

Expected result:
----------------
<?xml version="1.0" encoding="ISO-8859-1"?>
<root>
  <txt1>?</txt1>
  <txt2></txt2>
  <txt3></txt3>
  <submit>go</submit>
</root>

Actual result:
--------------
Warning: dump_mem(): output conversion failed due to conv error in /usr/home/pog/public_html/test/form2.php on line 17

Warning: dump_mem(): Bytes: 0xE9 0x3C 0x2F 0x74 in /usr/home/pog/public_html/test/form2.php on line 17

Warning: dump_mem(): encoder error in /usr/home/pog/public_html/test/form2.php on line 17



if you look at html source: 

<br />
<b>Warning</b>:  dump_mem(): output conversion failed due to conv error
 in <b>/usr/home/pog/public_html/test/form2.php</b> on line <b>17</b><br />
<br />
<b>Warning</b>:  dump_mem(): Bytes: 0xE9 0x3C 0x2F 0x74
 in <b>/usr/home/pog/public_html/test/form2.php</b> on line <b>17</b><br />
<br />

<b>Warning</b>:  dump_mem(): encoder error in <b>/usr/home/pog/public_html/test/form2.php</b> on line <b>17</b><br />
<?xml version="1.0" encoding="ISO-8859-1"?>
<root>
  <txt1>