方法拦截器、构造器

1. 方法拦截器 属性重载或方法重载

<?php
// __get(), __set(), __isset(),  __unset()用法
// 1.__get($name):当外部访问一个不存在或无权限访问的属性时，自动调用
class Product1
{
    public function __get($name)
    {
        return $name;
    }
}
$obj1 = new Product1();
echo $obj1->name;
echo $obj1->price;
echo '<hr>';
 // 2.__set()属性更新操作重定向
class Product2
{
    public function __set($name, $value)
    {
        echo $name. ':' .$value;
    }
}
$obj2 = new Product2();
$obj2->username = '小芳';
echo '<hr>';
//3. __isset()检查属性
class Product3
{
    public $username = '小刘';
    public function __isget($name)
    {
        echo $name. '小李';
        return isset($this->$name);
    }
}
$obj3 = new Product3();
var_dump(isset($obj3->username));
echo '<hr>';
var_dump(isset($obj3->price));
// 4.__unset()删除属性
class Product4
{
    public $name1 = '小明';
    private $name2 = '小六';
    public function __unset($name)
    {
        echo $this->$name ,'<hr>';
        // 访问内部私有属性
        unset($this->$name);
        echo $this->$name ,'<hr>';
    }
}
$obj4 = new Product4();
// 访问公共成员
echo '<hr>';
echo $obj4->name1;
echo '<hr>';
// 删除公共成员
unset($obj4->name1);
echo '<hr>';
// 外部访问内部私有属性
echo $obj4->name1;
unset($obj4->name2);

2. 实例演示查询构造器中的select(),inset(),update(),delete()四种方法

2.1 select()：方法

<?php
// 方法委托/方法拦截器 实战： 数据库查询构造器(链式查询)
// 查询类
class Query
{
    // 连接对象
    protected $db;
    // 数据表
    protected $table;
    // 字段列表
    protected $field;
    // 记录数量
    protected $limit;
    // 构造方法: 连接数据库
    public function __construct($dsn, $username, $password)
    {
        $this->connect($dsn, $username, $password);
    }
    // 连接数据库
    private function connect($dsn, $username, $password)
    {
        $this->db = new PDO($dsn, $username, $password);
    }
    // 设置默认的数据表名称
    public function table($table)
    {
        $this->table = $table;
        return $this;
    }
      // 设置默认的字段名称
      public function field($field)
      {
        $this->field = $field;
        return $this;
      }
    // 链式方法: 设置查询数量
    public function limit($limit)
    {
        $this->limit = $limit;
        return $this;
    }
    // 生成查询语句
    protected function getSql()
    {
        return sprintf('SELECT %s FROM %s LIMIT %s', $this->field, $this->table, $this->limit);
    }
    // 执行查询
    public function select()
    {
        return $this->db->query($this->getSql())->fetchAll(PDO::FETCH_ASSOC);
    }
}
// 数据据操作类
class DB
{
    // 静态方法委托
    public static function __callStatic($name, $args)
    {
        // 获取到查询类的对象: new Query()
        $dsn = 'mysql:host=localhost;dbname=phpedu';
        $username = 'root';
        $password = 'melinda123';
        $query = new Query($dsn, $username, $password);
        // 直接跳到Query类中的具体方法来调用
        return call_user_func([$query, $name], ...$args);
    }
}
$result = DB::table('users')
     // 字段列表
    ->field('id,name,email')
    ->limit(2)
    // 开始查询
    ->select();
print_r($result);

2.2 inset()：方法

<?php
//数据库插入构造器
class Query
{
    protected $pdo;
    protected $table;
    protected $field;
    protected $values;
    // 构造方法: 连接数据库
    public function __construct($dsn, $username, $password) 
    {
        $this->connect($dsn, $username, $password);
    }
    private function connect($dsn, $username, $password)
    {
        $this->pdo = new PDO($dsn, $username, $password);
    }
    public function table ($table)
    {
        $this->table = $table;
        return $this;
    }
    public function field ($field)
    {
        $this->field = $field;
        return $this;
    }
    public function values ($values)
    {
        $this->values = $values;
        return $this;
    }
    // 生成插入语句
    protected function sql()
    {
        return sprintf(' INSERT INTO %s (%s) VALUES (%s) ', $this->table, $this->field, $this->values);
    }
    // 执行
    public function insert()
    {
        $this->pdo->query($this->sql());
    }
}
class DB
{
    public static function __callStatic($name, $args)
    {
        $dsn = 'mysql:host=localhost;dbname=phpedu';
        $username = 'root';
        $password = 'melinda123';
        $query = new Query($dsn, $username, $password);
        return call_user_func([$query, $name], ...$args);
    }
}
$result = DB::table('users')
    -> field(`id,username,email,password`) 
    -> values("'飞猪', '123@qq.com', 'fz123'")
    -> insert();
echo $result ? '添加成功' :"添加失败";

2.3 update()：方法

<?php
//数据库更新构造器
class Query
{
    protected $pdo;
    protected $table;
    protected $set;
    protected $field;
    protected $values;
    protected $where;
    // 构造方法: 连接数据库
    public function __construct($dsn, $username, $password) 
    {
        $this->connect($dsn, $username, $password);
    }
    // 连接数据库
    private function connect($dsn, $username, $password)
    {
        $this->pdo = new PDO($dsn, $username, $password);
    }
    // 设置默认的数据表名称
    public function table ($table)
    {
        $this->table = $table;
        return $this;
    }
    public function set ($set)
    {
        $this->set = $set;
        return $this;
    }
      // 设置默认的字段名称
    public function field ($field)
    {
        $this->field = $field;
        return $this;
    }
    public function values ($values)
    {
        $this->values = $values;
        return $this;
    }
    public function where ($where)
    {
        $this->where = $where;
        return $this;
    }
    // 生成插入语句
    protected function sql ()
    {
        return sprintf("UPDATE %s SET %s =%s WHERE %s = %s", $this->field, $this->table, $this->values, $this->set, $this->where);
    }
    // 执行
    public function update ()
    {
        $this->pdo->query($this->sql());
    }
}
// 数据据操作类
class DB
{
    // 静态方法委托
    public static function __callStatic($name, $args)
    {
        $dsn = 'mysql:host=localhost;dbname=phpedu';
        $username = 'root';
        $password = 'melinda123';
        $query = new Query($dsn, $username, $password);
        return call_user_func([$query, $name], ...$args);
    }
}
$result = DB::table('users')
    ->set('username')
    ->values("'天猫'")
    ->field('id')
    ->where("'7'")
    ->update();
echo $result ? '更新成功' :"更新失败";

2.4 delete()：方法

<?php
//数据库删除构造器
class Query
{
    protected $pdo;
    protected $table;
    protected $field;
    protected $where;
    protected $values;
    // 构造方法: 连接数据库
    public function __construct($dsn, $username, $password) 
    {
        $this->connect($dsn, $username, $password);
    }
    // 连接数据库
    private function connect($dsn, $username, $password)
    {
        $this->pdo = new PDO($dsn, $username, $password);
    }
    // 设置默认的数据表名称
    public function table ($table)
    {
        $this->table = $table;
        return $this;
    }
      // 设置默认的字段名称
    public function field ($field)
    {
        $this->field = $field;
        return $this;
    }
    public function where ($where)
    {
        $this->where = $where;
        return $this;
    }
    public function values ($values)
    {
        $this->values = $values;
        return $this;
    }
    // 生成插入语句
    protected function sql ()
    {
        return sprintf(' DELETE FROM %s WHERE %s = %s', $this->table, $this->field, $this->values);
    }
    // 执行
    public function delete()
    {
        return $this->pdo->query($this->sql());
    }
}
// 数据据操作类
class DB
{
    // 静态方法委托
    public static function __callStatic($name, $args)
    {
        $dsn = 'mysql:host=localhost;dbname=phpedu';
        $username = 'root';
        $password = 'melinda123';
        $query = new Query($dsn, $username, $password);
        return call_user_func([$query, $name], ...$args);
    }
}
$result = DB::table('users')
    ->field('id')
    ->values(32)
    ->delete();
echo $result ? '删除成功' :'删除失败';