数据库查询构造器

数据库查询构造器

class Query()
{
   protected $db;//PDO连接对象
   protected $table;
   protected $field;
   protected $where;
   protected $Limit;
   protected $select;
   protected $toArray;
//连接数据库
private function connect($dsn,$username,$password)
{
  $this->db=new PDO($dsn,$username,$password);
}
function __construct($dsn,$username,$password)
{
   $this->connect($dsn,$username,$password);
}
//数据表方法$table
public function table($table)
{
    $this->table=$table;
    return $this;
}
//文件名方法$field
public function field($field)
{
    $this->field=$field;
    return $this;
}
//Limit方法$Limit
public function Limit($Limit)
{
    $this->Limit=$Limit;
    return $this;
}
//$where方法
public function where($where)
{
    $this->where=$where;
    return $this;
}
//$select方法
public function select($select)
{
    $this->select=$select;
    return $this;
}
public function getSql()
{
  return printf('SELECT %s FROM $s LIMIT %d',$this->table,$this->field,$this->limit);
}
//执行查询
public function select()
{
     return $this->db->query($this->getSql())->fetchAll(PDO::FETCH_ASSOC);
}
}
//工作类
class Db
{
   static function __callStatic($method,$args){
       $dsn='mysql:host=localhost;dbname=news';
       $username='root';
       $password='123456tyi';
       $query=new Query( $dsn, $username,  $password);
       //直接委托给query中的具体方法来完成
        return call_user_func([$query,$method],...args);
       }
}
    $res=Db::table('userid')->field('uid,uname')->Limit(1)->select();
    echo '<pre>';
    print_r($res);