PDO操作MySQL增删改查封装的类

封装类：

<?php
    class PDOClass{
        protected $pdo;
        //构造函数
        public function __construct()
        {
            $this -> pdo = new PDO('mysql:host=127.0.0.1;dbname=seven_month','root','root',array(PDO::ATTR_PERSISTENT));
        }
        //添加
        public function add($data){
            $res = $this -> pdo -> prepare("insert into seven_day values (null,?,?,?,?)");
            return $res -> execute($data);
        }
        //查询所有
        public function select_All($value){
            if (empty($value)){
                return $this -> pdo -> query('select * from seven_day') -> fetchAll(PDO::FETCH_ASSOC);
            }else{
                $res = $this -> pdo -> prepare("select * from seven_day like :value");
                $res -> bindValue(':value','%'.$value.'%');
                $res -> execute();
                return $res -> fetchAll(PDO::FETCH_ASSOC);
            }
        }
        //查询一条
        public function select_One($id){
            return $this -> pdo -> query("select * from seven_day where id = $id") -> fetch(PDO::FETCH_ASSOC);
        }
        //删除数据
        public function del($id){
            return $this -> pdo -> exec("delete from seven_day where id = $id");
        }
        //修改数据
        public function update($data){
            $res = $this -> pdo -> prepare("update seven_day set name = ? where id = ?");
            return $res -> execute($data);
        }
    }