function update($table,$arr,$arr0){
    $stm="";
    foreach ($arr as $key => $value) {
      $stm.= " $key = '$value' and";
    }
    $stm = substr($stm,0,-3);

    $stm0="";
    foreach ($arr0 as $key => $value) {
      $stm0.=" $key = '$value' and";

    }
    $stm0 = substr($stm0,0,-3);
    return $this->conn->query("UPDATE $table set $stm WHERE  $stm0");
  }