Is there any way to represent COLUMN NAME with a Variable in SQL-query?

Question

Is there any way to represent a column name of table with a variable?

Like in below example, in Switch - case: DATE, instead of writing column(visit_date), I want to use variable $d_status. Thanks in Advance.

    $s_id = mysql_prep($s_id);
    $d_status = "visit_date";
    $searchby = mysql_prep($searchby);
    $searchtext = mysql_prep($searchtext);

    $query  = "SELECT * ";
    $query .= "FROM doctor ";
    $query .= "WHERE (s_id = $s_id ) AND (d_status = '{$d_status}') ";

    switch ($searchby){
        case 'd_name':
        $query .= "AND ( d_name = '{$searchtext}' )";
        break;
        case 'd_id':
        $query .= "AND ( d_id = $searchtext )";
        break;
        case 'DATE':
        $query .= "AND ( $d_status = '{$searchtext}' )";
        break;
        Default: null;
        break;
        $result = mysqli_query($connection, $query);
        confirm_query($result);
        return $result;
    }