Double action ?

action="cgi-bin/FromLog.php?action=1"

<?php
if(isset($_GET['action']){
  switch($_GET['action']){
    case "accueil":
      //script a faire pour l'accueil
      break;
    case "page1":
      //script a faire pour la page1
      break;
    default:
      //script a faire pour l'accueil (par exemple, la page par default)
  }
}else{
  echo "Vous ne devriez pas être là."
}
?>

if(isset($_GET['action']){
  switch($_GET['action']){
	case "Add":
	include ("../classes/MMembers.class.php");
// Création d'un nouvel utilisateur 

	$error = false;
	$AddOK = false;
	$rights= 1 ;
	//echo'<pre>';print_r($_POST);echo'</pre>';
	if (isset($_POST['Add'])) 
	{
		$member = new MMembers();
		//$member->user_exists($_POST['email']);
		$exist = $member->Who_I_Am($_POST['email']);
		$Passwd = md5($_POST['PASSWD_MEMBER']);
		$Passwd2 = md5($_POST['PASSWD_MEMBER2']);
		if(empty($exist['0']))
		{
			if($Passwd == $Passwd2)	
			{	
			
				$member->Add_Member($_POST['organisateur'], 
									$_POST['adresse'], 
									$_POST['code_postal'],
									$_POST['ville'], 			
									$_POST['tva'],				
									$_POST['prenom'],
									$_POST['nom'],
									$_POST['email'],				
									$_POST['telephone'], 		
									$_POST['fax'], 				
									$Passwd, 								
									$rights);		
				$AddOK = true;
			}
			else 
			
			{
				$error = true;
			}
		}
		else 
		{
			$error = true;
		}
	
		if ($AddOK)
		{
			session_start();
			
			echo'<pre>';print_r($exist);echo'</pre>';
			echo'<pre>';print_r($exist['0']);echo'</pre>';
			echo'<pre>';print_r($exist['0']['0']);echo'</pre>';
		
			$USR = $member->Who_I_Am($_POST['email']);
			$_SESSION["USR_ID"] = $USR['0'];
			$_SESSION["PRENOM"]	=$_POST['prenom'];
			$_SESSION["NOM"]	=$_POST['nom'];
			$_SESSION["ADRS"]	=$_POST['adresse'];
			$_SESSION["CP"]		=$_POST['code_postal'];
			$_SESSION["VILLE"]	=$_POST['ville'];
			$_SESSION["BOITE"]	=$_POST['organisateur'];
			$_SESSION["MAIL"]	=$_POST['email'];
			$_SESSION["TEL"]	=$_POST['telephone'];
			$_SESSION["FAX"]	=$_POST['fax'];
			$_SESSION["TVA"]	=$_POST['tva'];
			$_SESSION["RIGHTS"] = '1';
			
		
			header("Location: ../panier_presta.php");
		}
		if ($error)
		{
			header("Location: ../commandeErno.php");
		
		}

	}
	break;
    case "Log":
      $ConnectOK = false;
    $error = false;
	//echo ("test");

    if (isset($_POST['login']) && $_POST['PASSWD_MEMBER']  && $_POST['MAIL'] != null)
    {
		$paswd = md5($_POST['PASSWD_MEMBER']);
        $member = new MMembers();
        if ($ID = $member->Connect_Me($_POST['MAIL'], $paswd))
        {
			session_start();
			//echo ($ID['0']);
        	$_SESSION["USR_ID"]=$ID['0'];
			$info = $member->Get_MemInfo();
			$_SESSION["PRENOM"]	=$info['0']['0'];
			$_SESSION["NOM"]	=$info['0']['1'];
			$_SESSION["ADRS"]	=$info['0']['2'];
			$_SESSION["CP"]		=$info['0']['3'];
			$_SESSION["VILLE"]	=$info['0']['4'];
			$_SESSION["BOITE"]	=$info['0']['5'];
			$_SESSION["MAIL"]	=$info['0']['6'];
			$_SESSION["TEL"]	=$info['0']['7'];
			$_SESSION["FAX"]	=$info['0']['8'];
			$_SESSION["TVA"]	=$info['0']['9'];
			$_SESSION["RIGHTS"] =$info['0']['10'];
            $ConnectOK = true;
        }
        else
        {	
            header("Location: ../debug.php");
        }
    }
    else
    {
        $error = true;
    }
    
    if ($ConnectOK)
    {
        header("Location: ../session_util.php");
    }
    if ($error)
    {
        header("Location: ../debug.php");
    }
      break;
    case "Deconection":
      session_start();
		 //destruction de toutes les variable de sessions
		session_unset() ;
		//destruction de la session
		session_destroy() ;
		header("Location: deco.html");
      break;
    default:
      break;
  }

<form enctype="multipart/form-data" method="POST" name="form" action="cgi-bin/FromUser?action=Add.php">
<center><input type="submit" name="Add" value="Enregistrement et passage à la deuxième étape" onClick="return CheckInput();" /></center>

<form enctype="multipart/form-data" method="POST" name="form" action="cgi-bin/FromUser?action=Log.php">
<center><input type="submit" name="Log" value="Connexion et passage à la deuxième étape"/></center>