email validation one condition & more than one else statement in PHP

I will try to put email validation with have more than one case. First(if):email is required. Second(if): invalid format of email. Third(else): Email is exist(Active User) Fourth(else): Email is in approve(Admin is not approved account yet so its still in request table) Fifth(else):Everything goes well,post the data into database.

I try to solve this by if-else statement but in last two case I do not have any condition its just have to pass that validation.I also try switch statement, but it's not go after the first case:

Here is my validation:

   if(empty($_POST['email']))
     {
         $email=$_POST['email'];
         $emailError="Email is required";
         $error=true;
        if(!filter_var($email, FILTER_VALIDATE_EMAIL)) {
            $emailError = "Invalid email format";
            $error=true;
          }
          else{
                 $sql="SELECT * FROM user WHERE email='$email'";
                 $res=mysqli_query($db,$sql);
                 if (mysqli_num_rows($res) > 0)
                 {
                 $emailError = "Email already exists";
                 $error=true;
                 }
               }

         else {
            $sl="SELECT * FROM request WHERE email='$email'";
             $ress=mysqli_query($db,$sl);
             if (mysqli_num_rows($ress) > 0)
             {
             $emailError = "Your Accout is in process";
             $error=true;
             }
           }
  }   

  else {
        $email=$_POST['email'];
       }