我正在努力使用面向 MYSQL 的 PDO，在 PHP 中使用 OO 编码生成一个体面的注册、登录和注销。
我收到错误消息：
注意：未定义的变量：第 34 行 D:\xampp\htdocs\dan\classes\DB.class.php 中的 db
致命错误：在第 34 行对 D:\xampp\htdocs\dan\classes\DB.class.php 中的非对象调用成员函数 query()
这是我的数据库类文件..
class DB {
protected $db_name = 'test';
protected $db_user = 'root';
protected $db_pass = '' ;
protected $db_host = 'localhost';
//***************** OPEN connection to database *****************
// Ensure called on every page that needs db connection
public function connect() {
try {
// Call PDO class
$db = new PDO('mysql:host='.$this->db_host.';dbname='.$this->db_name, $this->db_user, $this->db_pass);
}
catch(PDOException $e) {
// If error, nice error message here
echo $e->getMessage();
}
return true;
}
//******** SELECT rows from database *****************
// Returns a full row or rows from $table using $where as the where clause
// Return value is associative array with column names as keys
public function select($table, $where)
{
$query = $db->query('SELECT * FROM $table WHERE $where');
$result = $query->fetchAll(PDO::FETCH_ASSOC);
$num_rows = $result->rowCount();
// if only one result, return that single result
if($num_rows == 1)
{return $result[0];}
// but if numerous results, return the array
return $result;
}
//*********** UPDATE a row in database *****************
// Takes array of data, where keys in array are column names
// Value is the data to be inserted into columns
// $table is the name of the table and $where is the SQL WHERE clause
public function update($data, $table, $where) {
foreach ($data as $column => $value) {
$sql = "UPDATE $table SET $column = $value WHERE $where";
try{
$db->query($sql);
}
catch(PDOException $ex){
echo "error, ".$ex->getMessage();
}
}
return true;
}
//***************** INSERT a new row into database *****************
// Takes array of data, keys in array are column names
// Values are data to be inserted into columns
// $table is the name of table
public function insert($data, $table) {
$columns = "";
$values = "";
foreach ($data as $column => $value) {
$columns .= ($columns == "") ? "" : ", ";
$columns .= $column;
$values .= ($values == "") ? "" : ", ";
$values .= $value;
}
$sql = "INSERT INTO $table ($columns) VALUES ($values)";
try{
$db->query($sql);
}
catch(PDOException $ex){
echo "error, ".$ex->getMessage();
}
// return the ID of the user in the database
return $db->lastInsertId();
}
}
这是我的用户类：
// User.class.php
// User object represents a person
require_once 'DB.class.php'; // note: outside of class
class User {
public $id;
public $username;
public $hashedPassword;
public $email;
public $joinDate;
// Constructor is called whenever new object is created
// Takes an associative array with db row as argument, keys are columns in table
function __construct($data) {
$this->id = (isset($data['id'])) ? $data['id'] : "";
$this->username = (isset($data['username'])) ? $data['username'] : "";
$this->hashedPassword = (isset($data['password'])) ? $data['password'] : "";
$this->email = (isset($data['email'])) ? $data['email'] : "";
$this->joinDate = (isset($data['joinDate'])) ? $data['joinDate'] : "";
}
public function save($isNewUser = FALSE) {
// create new db object
$db = new DB();
// if the user is already registered, just an update
if(!$isNewUser) {
// set the data array
$data = array(
"username" => "'$this->username'",
"password" => "'$this->hashedPassword'",
"email" => "'$this->email'"
);
// update the row in database
$db->update($data, 'users', 'id = ' . $this->id);
}
// if user being registered
else {
$data = array(
"username" => "'$this->username'",
"password" => "'$this->hashedPassword'",
"email" => "'$this->email'",
"join_date" => "'".date("Y-m-d H:i:s",time())."'"
);
$this->id = $db->insert($data, 'users');
$this->joinDate = time();
}
return true;
}
} // end of class
这是我的 UserTools 类：
// UserTools.class.php
require_once 'User.class.php';
require_once 'DB.class.php';
class UserTools {
// Log in user (REQUIRES DB)
// First checks if username and password match row in db
// If yes, set session vars and store user object within
public function login($username, $password)
{
$db = new DB();
$db->connect();
// need to change to PREPARE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
$hashedPassword = md5($password);
$result = $db->query("SELECT * FROM users WHERE username = '$username' AND password = '$hashedPassword'");
if($result->rowCount() == 1)
{
$_SESSION['user'] = serialize(new User($result));
$_SESSION['login_time'] = time();
$_SESSION['logged_in'] = 1;
return TRUE;
}
else
{
return FALSE;
}
}
// Log the user out (destroy session vars)
public function logout() {
unset($_SESSION['user']);
unset($_SESSION['login_time']);
unset($_SESSION['logged_in']);
session_destroy();
}
// Check if username exists (called during registration) (REQUIRES DB)
public function CheckUsernameExists($username) {
$db = new DB();
$db->connect();
// CHANGE TO PREPARE !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
$result = $db->select("users","username=".$username);
if(($result->rowCount()) == 0)
{
return FALSE;
}
else
{
return TRUE;
}
}
// Get a user
// Returns a User object, takes user id as input
public function get($id) {
// unsure if to delete the following:
$db = new DB();
$db->connect();
$result = $db->select('users', "id = $id");
return new User($result);
}
} // end of class
请告诉我哪里出错了。我显然不理解面向对象的编码，即使是在一个又一个例子又一个例子又一个例子之后。
我只想创建一个有效的注册系统，并且采用模块化、OO 风格的代码。