$POST

$valeur1 = $_POST['mon_champ'];
          $valeur2 = $_POST['mon_champ'];
	  $valeur3 = $_POST['mon_champ'];
          $valeur4 = $_POST['mon_champ'];

if ($valeur1 =="Option 1"){
header('Location: http://*****/page2.php');	
exit;
}

session_start();
$_SESSION['formulaire'] = $_POST;
// Code de ton script
header('Location: http://......./page2.php');

session_start();
$post = $_SESSION['formulaire']; // On traite alors $post comme si c'était $_POST
// Suite du code

<form action="page2.php" method="post" name="donnees" id="donnees">
<input type="radio" name="mon_champ" value="Option 1"/>
                      <strong>1</strong><br>
<input type="radio" name="mon_champ" value="Option 2"/>
                      <strong>2</strong><br>
<input type="radio" name="mon_champ" value="Option 3"/>
                      <strong>3</strong><br>

<input type="submit" name="Submit" value="Continuer">                      

if ($valeur1 =="Option 1"){
session_start();

$_SESSION['donnees'] = $_POST;
header('Location: http://*******/page1.php');	
exit;
}

//initialize the session
session_start();
$date=date("d-m-Y");

[color=orange]//*** j'ai essayé : ***[/color]
$post = $_POST['donnees']; 

[color=orange]//*** et j'ai essayé :***[/color]
$post = $_SESSION['donnees'];