function Update($mysqli,$table_name, $form_data, $where_clause='',$v=0){   

  $whereSQL = '';

  if(!empty($where_clause)){

    // check to see if the 'where' keyword exists

    if(substr(strtoupper(trim($where_clause)), 0, 5) != 'WHERE'){

        // not found, add key word

      $whereSQL = " WHERE ".$where_clause;

    } else {

      $whereSQL = " ".trim($where_clause);

    }

  }

  // start the actual SQL statement

  $sql = "UPDATE `".$table_name."` SET ";

  // loop and build the column /

  $sets = array();

  foreach($form_data as $column => $value) {

    $sets[] = "`".$column."` = '".$value."'";

  }

  $sql .= implode(', ', $sets);

  // append the where statement

  $sql .= $whereSQL;

  // run and return the query result

  if($v==1) {

    echo $sql."<br>";

  }

  return mysqli_query($mysqli,$sql);

}