单例模式（数据库crud操作）

单例模式（数据库crud操作）

作业标题：0813 oop编程-3
作业内容：参考demo3.php, 完善数据库查询构造器其他的操作，update,delete,insert

---

• insert,delete,update

interface iDbBase
{
    //数据库操作 curd
    static function insert($db,$data);
    static function select($db,$where=[]);
    static function delete($db,$where=[]);
    static function update($db,$data,$where=[]);
    static function doConnect($dsn,$username,$password);
}
abstract class aDb implements iDbBase
{
    // 创建类的唯一实例 pdo对象
    private static $_instance;
    // private私有的 阻止此类在外部进行实例化
    private function __construct()
    {
    }
    // private私有的 阻止此类在外部进行克隆
    private function __clone()
    {
    }
    static function doConnect($dsn,$username,$password)
    {
        // 得到pdo连接对象 储存在 $_instance
        if(is_null(self::$_instance))
        {
            self::$_instance = new PDO($dsn,$username,$password);
        }
        return self::$_instance;
    }
}
// 工作类
class Db extends aDb{
    //数据库操作 curd
    static function insert($db,$data){
        return $db->query($data);
    }
    static function select($db,$where=['empno'=>7369]){
        // select filed.. form tableName where gender=1 and id>1
        // select filed.. form tableName where gender=1
        $str = '';
        foreach($where as $k=>$v)
        {
            if(is_array($where))
            {
                if(count($where) > 1)
                {
                    $str .= $k . ' = ' . $v . ' and ';
                }else{
                    $str .= $k . '=' . $v;
                }
            }
        }
        if(count($where) > 1)
        {
            // 去掉where中的最后一个and
            $str = substr($str,0,strlen($str)-4);
            // echo $str;
        }
            echo $str;
            // SELECT `uname`, `tel` FROM `iuser` WHERE gender = 1 and id = 20201
        return $db->query("SELECT `ename`, `job` FROM `emp` WHERE $str ")->fetchAll(PDO::FETCH_ASSOC);
    }
    static function delete($db,$where=['empno'=>7936]){
        //DELETE FROM Persons WHERE LastName='Griffin'
        $str = '';
        foreach($where as $k=>$v)
        {
            if(is_array($where))
            {
                if(count($where) > 1)
                {
                    $str .= $k . ' = ' . $v . ' and ';
                }else{
                    $str .= $k . '=' . $v;
                }
            }
        }
        if(count($where) > 1)
        {
            // 去掉where中的最后一个and
            $str = substr($str,0,strlen($str)-4);
            // echo $str;
        }
            echo $str;
            // DELETE FROM Persons WHERE LastName='Griffin'
        return $db->query("DELETE FROM `emp` WHERE $str ")->fetchAll(PDO::FETCH_ASSOC);
    }
    static function update($db,$data=1000,$where=['empno'=>7938]){
        $str = '';
        foreach($where as $k=>$v)
        {
            if(is_array($where))
            {
                if(count($where) > 1)
                {
                    $str .= $k . ' = ' . $v . ' and ';
                }else{
                    $str .= $k . '=' . $v;
                }
            }
        }
        if(count($where) > 1)
        {
            // 去掉where中的最后一个and
            $str = substr($str,0,strlen($str)-4);
            // echo $str;
        }
            echo $str;        
            // UPDATE Persons SET Age=36 WHERE FirstName='Peter' AND LastName='Griffin'
        return $db->query("UPDATE `emp` SET salary=$data WHERE $str ");
    }
}
$dsn = 'mysql:host=localhost;dbname=my_test';
$db = Db::doConnect($dsn,'root','root');
$data="INSERT INTO emp "."(empno,ename,job,mgr,hiredate,salary,comm,deptno)"."VALUES"."('7938','张同','职员','7900','2012-08-07',3000,400,30)";
print_r(Db::select($db));
print_r(Db::insert($db,$data));
print_r(Db::delete($db));
print_r(Db::update($db));