Ok here comes a safe solution as I find out the ping time on the net could create a mess if several users would rewrite the same file to reuse it as a database immediately (tell me if I'm wrong, it seems logical):
Php (my Simpleviewer is embedded) :
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/swfobject/2.2/swfobject.js"></script>
<script type="text/javascript">
var flashvars = {};
flashvars.galleryURL = "gallery/<?php echo $_GET['exposition']; ?>_GA.xml";
var params = {};
params.allowfullscreen = true;
params.allowscriptaccess = "always";
params.wmode = "transparent";
swfobject.embedSWF("simpleviewer.swf", "flashContent", "800", "600", "9.0.124", false, flashvars, params);
</script>
</head>
<body>
/* FIRST CREATING THE GALLERY */
<?php
$exposition = $_GET['exposition'];
$xslt = new XSLTProcessor();
$xml = new domDocument();
$xml -> load('expographie_v041109.xml');
$xsl = new domDocument();
$xsl -> load('gallery_generator.xslt');
$xslt -> importStylesheet($xsl);
$xslt -> setParameter(null,'exposition',$exposition);
$xslt -> transformToURI($xml,'gallery/'.$exposition.'_GA.xml');
/*THEN CREATING THE PAGE WHERE SIMPLEVIWER IS EMBBED */
$xslt = new XSLTProcessor();
$xml = new domDocument();
$xml -> load('expographie_v041109.xml');
$xsl = new domDocument();
$xsl -> load('exposition_unique_index.xslt');
$xslt -> importStylesheet($xsl);
$xslt -> setParameter(null,'exposition',$exposition);
echo $xslt -> transformToXml($xml);
?>
?>
</body>
</html>
gallery_generator.xslt :
<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:output method="xml" encoding="utf-8" indent="yes" />
<xsl:param name="exposition" />
<xsl:template match="EXPOSITION">
<xsl:if test="@ID_EXPOSITION[self::node()=$exposition]">
<simpleviewergallery maxImageWidth="1200" maxImageHeight="800" textColor="0x444444" frameColor="0xFFFFFF" frameWidth="0" galleryStyle="Modern" stagePadding="2" navPadding="40" thumbColumns="2" thumbRows="5" thumbPosition="right" vAlign="center" hAlign="center" title="{@TITRE}" enableRightClickOpen="false" backgroundImagePath="" imagePath="" thumbPath="">
<xsl:apply-templates select="VISUEL_NUMERISE_ET_PUBLIABLE" />
</simpleviewergallery>
</xsl:if>
</xsl:template>
<xsl:template match="VISUEL_NUMERISE_ET_PUBLIABLE">
<xsl:for-each select="@FICHIER_CONSULTABLE">
<image>
<filename><xsl:value-of select="."/></filename>
<caption><xsl:value-of select="../@LEGENDE"/></caption>
</image>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
and the page where simpleviewer is called : exposition_unique_index.xslt
<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0"
xmlns:php="http://php.net/xsl">
<xsl:output method="html" encoding="ISO-8859-1" indent="yes" />
<xsl:param name="exposition" />
<xsl:template match="EXPOSITION">
<xsl:if test="@ID_EXPOSITION[self::node()=$exposition]">
<div id="flashContent">SimpleViewer requires JavaScript and the Flash Player.
<a href="http://www.adobe.com/go/getflashplayer/">Get Flash.</a></div>
</xsl:if>
</xsl:template>
</xsl:stylesheet>