使用接口操作数据库

抽象类和接口：

• 抽象类:不能直接实例化，可以在类中定义方法和属性。类似于模版，子类继承后再实现详细功能.
• 接口: 接口中定义的所有方法都必须是公有,接口本身是抽象的，内部申明的方法也是抽象的； 不用加abstract,接口不能有属性、普通方法、可以有常量.

使用接口来操作数据库

<?php
$config = require 'config.php';
//定义接口类
interface iDB
{
// 增加
    public static function insert($pdo, $data);
// 删除
    public static function delete($pdo, $where);
// 查询
    public static function select($pdo, $options = []);
// 修改
    public static function update($pdo, $options);
}
//定义抽象类实现接口，封装公共数据库连接方法
abstract class aDB implements iDB
{
    protected static $pdo;
    //数据库连接方法
    public static function conn($dsn, $user, $pwd)
    {
        //判断数据库连接对象是否存在
        if (is_null(self::$pdo)) {
            try {
                  $pdo = new PDO($dsn, $user, $pwd);
                // 设置结果集的默认获取模式
                $pdo->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
                return $pdo;
            } catch (PDOException $e) {
                exit('Connection Error: ' . $e->getMessage());
            }
        }
        return self::$pdo;
    }
}
//实现类，实现接口中的方法
class DB extends aDB
{
    // 增加
    public static function insert($pdo, $data)
    {
        $sql = "INSERT INTO `users`(`name`,`pwd`,`age`,`tel`) VALUES (?,?,?,?)";
        $stmt = $pdo->prepare($sql);
        $stmt->bindParam(1, $name, PDO::PARAM_STR, 50);
        $stmt->bindParam(2, $pwd, PDO::PARAM_STR, 50);
        $stmt->bindParam(3, $age, PDO::PARAM_INT, 30);
        $stmt->bindParam(4, $tel, PDO::PARAM_STR, 50);
        $num = 0;
        foreach ($data as $user) {
            extract($user);
            $stmt->execute() or die(print_r($stmt->errorInfo(), true));
            if ($stmt->rowCount() > 0) {
                $num += $stmt->rowCount();
            }
        }
        printf("成功添加 %s 条数据", $num);
    }
// 删除
    public static function delete($pdo, $where)
    {
        $sql = "delete from `users` where `id` = ? ";
        $stmt = $pdo->prepare($sql);
        $stmt->bindParam(1, $where);
        $stmt->execute() or die(print_r('删除失败' . $stmt->errorInfo(), true));
        printf("成功删除%s条数据", $stmt->rowCount());
    }
// 查询
    public static function select($pdo, $options = [])
    {
        $sql = "select `id`,`name`,`age` from `users` where id>= ?";
        $stmt = $pdo->prepare($sql);
        $stmt->bindParam(1,$options, PDO::PARAM_INT, 30);
        $stmt->execute() or die(print_r('查询失败' . $stmt->errorInfo()));
        foreach ($stmt->fetchAll() as $user) {
                 vprintf("id:%s,name:%s,age:%s<br>", $user);
        }
    }
// 修改
    public static function update($pdo, $options)
    {
        $sql = "update `users` set `name`=?  where id=? ";
        $stmt = $pdo->prepare($sql);
        $stmt->bindParam(1, $options['name'], PDO::PARAM_STR, 50);
        $stmt->bindParam(2, $options['id'], PDO::PARAM_INT, 20);
        $stmt->execute() or die(print_r('更新数据失败:' . $stmt->errorInfo()));
        if ($stmt->rowCount() > 0):
            print_r('成功更新' . $stmt->rowCount() . '条数据');
        endif;
    }
}
extract($config);
$dsn = "$type:host=$host;dbname=$dbname;charset=$charset;port=$port";
$pdo = DB::conn($dsn, $username, $password);
$users = [
    ['name' => 'Adalia1', 'age' => 33, 'pwd' => sha1('1256'), 'tel' => '188938801'],
    ['name' => 'Brenda1', 'age' => 12, 'pwd' => sha1('12456'), 'tel' => '178922801'],
    ['name' => 'Alice1', 'age' => 55, 'pwd' => sha1('12346'), 'tel' => '168448801'],
    ['name' => '骑牛狂奔1', 'age' => 65, 'pwd' => sha1('13456'), 'tel' => '138966801'],
    ['name' => 'Catherine1', 'age' => 111, 'pwd' => sha1('23456'), 'tel' => '118988801'],
];
//增加
//DB::insert($pdo, $users);
//删除
//DB::delete($pdo,110);
//查询
//DB::select($pdo,88);
//更新
DB::update($pdo,['name'=>'赵四333','id'=>118]);

总结:初步了解了接口和抽象类的定义和使用方法，但是对接口和抽象类在开发中的使用时机还不是很理解。