TableTools and server side

Hi everybody,

I use Table tools like this :

TableTools.BUTTONS.download = {
	"sAction": "text",
	"sTag": "default",
	"sFieldBoundary": "",
	"sFieldSeperator": "\t",
	"sNewLine": "<br>",
	"sToolTip": "",
	"sButtonClass": "DTTT_button_text",
	"sButtonClassHover": "DTTT_button_text_hover",
	"sButtonText": "Download",
	"mColumns": "all",
	"bHeader": true,
	"bFooter": true,
	"sDiv": "",
	"fnMouseover": null,
	"fnMouseout": null,
	"fnClick": function( nButton, oConfig ) {
		var oParams = this.s.dt.oApi._fnAjaxParameters( this.s.dt );
		var iframe = document.createElement('iframe');
		iframe.style.height = "0px";
		iframe.style.width = "0px";
		iframe.src = oConfig.sUrl+"?"+$.param(oParams);
		document.body.appendChild( iframe );
	},
	"fnSelect": null,
	"fnComplete": null,
	"fnInit": null
};

$(document).ready(function() {
	// Affichage du tableau avec le détail des entrées
	$('#tabDetail').dataTable({
		"bProcessing": true,
		"bServerSide": true,
		"sDom": 'T<"clear">lfrtip',
		"oTableTools": {
			"aButtons": [{
				"sExtends": "download",
				"sButtonText": "Download CSV",
				"sUrl": "generate_csv.php"
			}]
		},
		"sAjaxSource": "serverSide_general.php",
		"fnServerData": function( sUrl, aoData, fnCallback ) {
            $.ajax( {
                "url": sUrl,
                "data": aoData,
                "success": fnCallback,
                "dataType": "json",
                "cache": false
            } );
        }
})

And my generate_csv.php :

<?php
header('Content-Type: application/csv-tab-delimited-table');
header('Content-Disposition: attachment');

$csv = '"Usager";"Prénom";"Prénom";"Prénom";"Prénom";"Prénom";"Email"'."\n";

echo json_encode($csv);

exit;
?>

But, when i click on Download CSV, there's nothing happened.

Any idea ?

Magali