hello dears friends
i get a error on my page but i don't know what i do wrong
the error code is "Notice: Undefined index: MM_Username in c:\folder\page.php on line

<form name="form1" method="POST" action="<?php echo $editFormAction; ?>">
        <label for="textfield"></label>
        <input name="article" type="text" id="article" value="<?php echo $row_N9389['article']; ?>" readonly><br>
        <label for="price"></label>
        <input name="prix" type="text" id="prix" value="<?php echo $row_N9389['prix']; ?>" readonly><br>
        <label for="Qtty"></label>
         <input name="quantity" type="number" max="15" min="1" value="1"><br>
        <input type="hidden" name="usercookie" id="usercookie" value="<?php echo $_SESSION['MM_Username']; ?>">
        <input type="hidden" name="sku" id="sku" value="<?php echo $row_N9389['sku']; ?>">
<input type="submit" name="button" id="button" value="ADD TO SHOPPING CART">
<input type="hidden" name="MM_insert" value="form1">
      </form>

and on top of my page i have <?php session_start (); ?>

i noticed when user is connect it don't show the erro message i would like to don't show anythink if user is not connect.