Problem when adding special characters to an XML file

[te0t3l <te0t3l@xxxxxxxxx>]

Hi, I'm editing an XML file through a form:

$XML = new DOMDocument('1.0', 'UTF-8');
$XML->preserveWhiteSpace = false;
$XML->load("../xml/exposiciones.xml");
$raiz = $XML->documentElement;

$nodoContenedor = $XML->getElementsByTagName('texto');
        foreach ($nodoContenedor as $NuevoNodo)
            {
                //titulo
                $nodoTitulo = $XML->createElement("p",
""$titulo"");
                $NuevoNodo->appendChild($nodoTitulo);
                $nodoTitulo->setAttribute("class", "titulo");
                $NuevoNodoHijo = $XML->createElement("subtitulo", "
$subtitulo");
                $nodoTitulo->appendChild($NuevoNodoHijo);
                $raiz->appendChild($NuevoNodo);
}

$NodoRefTitulo = $XML->getElementsByTagName('p')->item(0);
$NodoRefTitulo->parentNode->insertBefore($nodoTitulo, $NodoRefTitulo);
$XML->formatOutput = true;
$XML->save("../xml/exposiciones.xml");


The problem is that the special characters that I introduce through the form
(á,é,ó...) corrupt the XML file, and when I try to update again the file,
receipted this error:

Warning: DOMDocument::load() [domdocument.load]: Input is not proper UTF-8,
indicate encoding ! Bytes: 0xF3 0x6E 0x20 0x63 in........

I'd try to fix up it with the label <![CDATA[]]>, and by changing the
encoding -> UTF-8, iso-8859-1 as well,

here: $XML = new DOMDocument('1.0', 'UTF-8'); --> $XML = new
DOMDocument('1.0', 'iso-8859-1');

and in the XML file:

<?xml version="1.0" encoding="utf-8"?> .....

and also I was try:

$subtitulo = str_replace("ó" , "&#243;", utf8_encode($subtitulo));
$subtitulo = str_replace("ó" , "&oacute;;", utf8_encode($subtitulo));

When I open the XML file again i found an strange character between "i" and
"n" exposicion (exposición):

<p class="titulo">"A-foto"<subtitulo> *exposiciﻩn*colectiva.</subtitulo></p>


Anyone know how to solve this problem?

Thanks for your help,

Te0