Checkboxes don t send to right url

When i check this form i always come to the google option, no matter which combination. i don t know what i am doing wrong. i m using the same form for checkboxes on an other case. 1-6 is always google. even not configurated multi-choices are google.

.pic{
        background: url("#") no-repeat;
        width:616px;
        height:525px;
        position: relative;
        }
    input[type="checkbox"] {
          transform:scale(1.3, 1.3);
        }
        .poin1{
        left: 548px;
        bottom:59px;
        position: absolute;
        }
        .poin2{
        left: 540px;
        bottom:155px;
        position: absolute;
        }
        .poin3{
        left: 500px;
        bottom:265px;
        position: absolute;
        }
        .poin4{
        left: 495px;
        bottom:325px;
        position: absolute;
        }
      .poin5{
        left: 479px;
        bottom:385px;
        position: absolute;
        }
      .poin6{
        left: 465px;
        bottom:460px;
        position: absolute;
        }



<form method="post" action="../includes/messung_jeans.php">  <div class="pic">
    <input type="checkbox" id="cb1" name="cb1" value="m1" class="poin1">
    <input type="checkbox" id="cb2" name="cb2" value="m2" class="poin2">
    <input type="checkbox" id="cb3" name="cb3" value="m3" class="poin3">
    <input type="checkbox" id="cb4" name="cb4" value="m4" class="poin4">
   <input type="checkbox" id="cb5" name="cb5" value="m5" class="poin5">
   <input type="checkbox" id="cb6" name="cb6" value="m6" class="poin6">


</div>
  <div class="buttonHolder">
<input type="submit" name="send" <a class="btn primary-button" value="Weiter" /> </a>

    </div>



<?

if($_POST['cb1'] == m1){
    header("Location: http://www.google.com");
}
elseif($_POST['cb2'] == m2 ){
    header("Location: http://www.yahoo.com");
}
elseif($_POST['cb2'] == m2 && $_POST['cb1'] == m1 ){
    header("Location: http://www.bild.de");
}
elseif($_POST['cb3'] == m3 ){
    header("Location: http://www.bing.com");
}
elseif($_POST['cb4'] == m4 ){
    header("Location: http://www.bing.com");
}
elseif($_POST['cb5'] == m5 ){
    header("Location: http://www.bing.com");
}
elseif($_POST['cb6'] ==  m6 ){
    header("Location: http://www.bing.com");
}

else {
    header("Location: http://ift.tt/2g3DGog");
}  
?>