Blabla plus haut avec ma chaine de connexion SQL qui fonctionne désormais
//creation of the application controller
$_SESSION['controller']= new ControllerImpl();

$ctrl = $_SESSION['controller'];
//----------------------
//Action management
//----------------------

if(!isset($_REQUEST['action'])){
    echo " pas isset";
    $request = new Request($_REQUEST);
    $response = new Response();
    echo " 1 ";
    $listener = $ctrl->getListener("default");
    echo "classe : ".get_class($listener);
    $data = $listener->handle($request);
    echo $data;
    $view = $ctrl->getView("default");
    echo "pourp2";
    $view->display($data,$response);

<?php
echo " ok 1 ";
//-----------------------------------------------------------------------------
// includes des views
//-----------------------------------------------------------------------------
include_once 'Ecom/views/DefaultView.php';
include_once 'Ecom/views/ErrorView.php';
include_once 'Ecom/views/ActionView.php';
include_once 'Ecom/views/TaskView.php';
include_once 'Ecom/listeners/DefaultListener.php';
include_once 'Ecom/listeners/ActionListener.php';
include_once 'Ecom/listeners/TaskListener.php';

echo " ok 8 ";

$controller =$_SESSION['controller'];
echo " ok 9 ";
/**
*Pour chaque action que l'on passera dans l'URL, on associe une view et un listener
*/

//-----------------------------------------------------------------------------
// registration of the views and default error page
//-----------------------------------------------------------------------------

$controller->registerView ('default', new DefaultView());
echo " ok 10 ";
$controller->registerView ('error', new ErrorView());
echo " ok 11 ";
$controller->registerView ('action', new ActionView());
echo " ok 12 ";
$controller->registerView ('newAction', new ActionView());
echo " ok 13 ";
$controller->registerView ('task', new TaskView());
echo " ok 14 ";
//-----------------------------------------------------------------------------
// registration of the listeners
//-----------------------------------------------------------------------------
$controller->registerActionListener ('default', new DefaultListener());
$controller->registerActionListener ('action', new DefaultListener());
$controller->registerActionListener ('newAction', new ActionListener());
$controller->registerActionListener ('task', new TaskListener());
 ?>

<?php
echo "dv 1";

echo "dv 2";
include_once "Ecom/views/View.php";
include_once "Ecom/model/ActionPlanDAO.php";
include_once "Ecom/model/TaskDAO.php";
echo "dv 3";

/**
* Cette view est celle par défaut, elle appelé lorsqu'aucune action n'est spécifiée dans l'url
*/

class DefaultView implements View{
    /**
    * La fonction display permet d'affiche du contenu html dans la page
    * elle est appelé dans index.php
    * @param Data $data la donnée renvoyée par le handle des listeners
    * @param Response $response l'objet créé dans index.php
    */
    public function display(Data $data, Response $response){
        //----------------Action Part--------------------//
        $actionPlanDAO = new ActionPlanDAO();

        $result = $actionPlanDAO->_findAll();
        
        $xml_output  = '<?xml version="1.0" encoding="UTF-8"?>'.'<carnet>';
        while ($row = mysql_fetch_array($result)) {
            $xml_output .= '<truc>';
        }
        $xml_output .= '</carnet>';
        
        $fp = fopen("actionExport.xml", 'w+');
        fputs($fp, $xml_output);
        fclose($fp);
        $response->write("<br/>");
        $response->write('<div id="grid-example2"></div><a href="actionExport.xml">Voir le fichier XML</a><br/>');
    
        $link1 = "'index.php?action=action'";
        $response->write('<input type="button" value="View actions" name="action_link" onclick="self.location.href='.$link1.'" /><br/>');
        
        //---------------------Task Part---------------------//
        $taskDAO = new TaskDAO();
        $result = $taskDAO->_findAll();
        
        $xml_output  = '<?xml version="1.0" encoding="UTF-8"?>'.'<carnet>';
        while ($row = mysql_fetch_array($result)) {
            $xml_output .= '<truc>';
        }
        $xml_output .= '</carnet>';
        
        $fp = fopen("taskExport.xml", 'w+');
        fputs($fp, $xml_output);
        fclose($fp);
        $response->write("<br/>");
        $response->write('<div id="grid-example"></div><a href="taskExport.xml">Voir le fichier XML</a><br/>');
        
        
        $link2 = "'index.php?action=task'";
        $response->write('<input type="button" value="View tasks" name="task_link" onclick="self.location.href='.$link2.'" />');
        $response->write("<br/><br/>");
        
        
    }
}

Je confirme, le code est bizarre ...

<?php
class MySQLConnection
{
    private static $_instance;

    private function __construct()
    {
        echo "Construction de l'instance";
    }

    public static final function getInstance()
    {
        echo "je passe ici";
        if(!isset(self::$_instance))
        {
            self::$_instance = new MySQLConnection();
        }
        return self::$_instance;
    }
}

<?php
//...
    private function _construct(){
        echo "construct";
        $this->isconnected=false;
    }

<?php
//...
    private function __construct(){
        echo "construct";
        $this->isconnected=false;
    }

<?php

//--------------------------
//Include files
//--------------------------

//configuration file
include_once './config.php';

echo $init_file;

//framework classes and interfaces
include_once $root_app.'Ecom/views/View.php';
include_once $root_app.'Ecom/views/ActionView.php';
include_once $root_app.'Ecom/views/TaskView.php';
include_once $root_app.'Framework/ControllerImpl.php';
include_once ($root_app.'Framework/Data.php');
include_once ($root_app.'Framework/StringData.php');
include_once ($root_app.'Framework/Request.php');
include_once ($root_app.'Framework/Response.php');
include_once ($root_app.'Database/MySQLConnection.php');

//Connection with database
echo "1";
$connect = MySQLConnection::getInstance();
echo "2";
try{
	$connect->connect();
	echo "connecté";
}catch (ConnectionException $e){
	echo $e;
}
echo "youpi";
//---etc etc etc

<?php

include_once($root_app."Database/ConnectionException.php");
echo "je suis le fichier MySQLCOnnection";
class MySQLConnection {
	private $connectionId;
	private $dbconnection;
	private $isconnected;
	
	private function _construct(){
		echo "construct";
		$this->isconnected=false;
	}
	
	public static final function getInstance(){
		$instance = null;
		echo "je passe ici";
		if(!isset($isconnected)){
			$instance = new MySQLConnection();
		}else{
			$instance = $this;
		}
		return $instance;
	}
	
	public function connect(){
		$this->connectionId = mysql_connect('toto.fr', 'root', '');
		echo "je passe dans la boucle de connexion";
		if (!$this->connectionId) {
    		die('Connexion impossible : ' . mysql_error());
		}
		$this->dbconnection = mysql_select_db('toto',$this->connectionId) or die('Database error');
		
		if(isset($this->connectionId) && $this->dbconnection){
			$this->isconnected = true;
		}else{
			$this->isconnected=false;
			throw new ConnectionException('Connection failed');
		}
	}