function delFile()
{
    $id = params("id");
    $file = File::getDocumentById($id);
    $status = $file->delete();
    set("status", $status);
    header('Content-Type: application/json');
    return render("status.json.php");
}
<?php

require_once "model_class_includes.php";
//header('Content-Type: application/json; charset=utf-8');
//$f = (File::getDocumentById(1));
//echo $f->getLibelle();
//echo "  éé@ç";
//echo json_encode(File::getAllDocumentByPromo("CSI_A1"));
$f = File::getDocumentById(100);
$f->setLibelle("fictest");
$f->setPromo("CSI_A1");
$f->setRang("20");
$f->setFichier("blabla.txt");