It works fine with uploadify on my sites ! But for a more concrete answer you have to supply additional informations on your code.
As a short draft you may take this, please consider about the session_id for symfony security.
jQuery("#myupload").uploadify({
'script' : '<?php echo url_for("model/upload")."?".ini_get("session.name") . "=" . session_id(); ?>',
'scriptData' : { "sf_user_id": '<?php echo $sf_user_id ?>' }
});
public function executeUpload($request){
if($request->isMethod("POST")){
foreach($request->getFiles() as $file){
/* do what you want with $file */
}
}
}
Good luck :-)