php switch statement

See following:  

switch(intval($_POST['ua'])) {
                        case ">=1":
                              $_SESSION['height'] = $_POST['bdepth'];
                              $_SESSION['width'] = $_POST['bwidth'];
                              $_SESSION['length'] = $_POST['blength'];
                              $_SESSION['cuft'] = $_POST['tsqft'];
                              $qryu = "UPDATE visitor set height = " . $_SESSION['height'] . ", width = " . $_SESSION['width'] . ", length = " . $_SESSION['length'] . ", cuft = " . $_SESSION['cuft'] . " where vid = " . $_SESSION['vid'];
                              echo "qryu = " . $qryu . "<br>";
                              $resu = mysqli_query($link, $qryu);
                              $_SESSION['step'] = "2";
                        break;
                              case ">=2":      
                              $_SESSION['filt'] = $_POST['filt'];
                              $qryu = "UPDATE visitor set filtertration = " . $_SESSION['filt'] . " where vid = " . $_SESSION['vid'];
                              $resu = mysqli_query($link, $qryu);
                              $_SESSION['step'] = "3";
                        break;
                  }            

I have this code in an instance where I know that the value of $_POST'ua'] is 1.

It does not execute the case ">=1".

Is this an illegal expression for "case"?

Thanks