Connect.class.php连接数据库(随时修改)

<?php
class Connect
{
    public $host = "localhost"; //服务器地址
    public $uid = "root"; //数据库的用户名
    public $pwd = "123"; //数据库的密 
    
    //执行SQL语句，返回相应结果的函数
    //$sql是要执行的SQL语句
    //$type是SQL语句的类型，0代表增删改，1代表查询
    //$db代表要操作的数据库
    
    
        //返回json数据
         public function  PDO_json($sql,$type=1,$db="mydb")
    {
              try
         {
            $dsn = "mysql:dbname=mydb;host=localhost";
            $pdo = new PDO($dsn,$this->uid,$this->pwd);
         }
              
              catch(Exception $e)
         {  
              echo "连接失败".$e->getMessage();      
         }
            
            $st = $pdo->prepare($sql);
            
            $result = $st->execute();
            
            if($type==1)
          {
            $att = $st->fetchAll(PDO::FETCH_ASSOC);
            
            return json_encode($att);
          }
              else
          {
                if($result)
            {
                return "OK";
            }
                    else
            {
                return "NO";
            }
          }
    }
        
        //返回二维数组
         public function  PDO_array($sql,$type=1,$db="mydb")
    {
              try
         {
            $dsn = "mysql:dbname=mydb;host=localhost";
            $pdo = new PDO($dsn,$this->uid,$this->pwd);
         }
              catch(Exception $e)
         {  
              echo "连接失败".$e->getMessage();      
         }
            
            $st = $pdo->prepare($sql);
            
            $result = $st->execute();
            
              if($type==1)
          {
            return $st->fetchAll(PDO::FETCH_NUM);
          }
              else
          { 
              //如果是其他语句，返回true或false
                if($result)
            {
                return "OK";
            }
                else
            {
                return "NO";
            }
          }
    }
    
            

     //返回字符串    
         public function PDO_string($sql,$type=1,$db="mydb")
    {    
    
                try
           {
              $dsn = "mysql:dbname=mydb;host=localhost";
              $pdo = new PDO($dsn,$this->uid,$this->pwd);
           }
           
                   catch(Exception $e)
     
           {  
                echo "连接失败".$e->getMessage();      
           }
            
                $st = $pdo->prepare($sql);
                
                $result = $st->execute();
            
              if($type==1)
          {
              return $st->fetchColumn();
          }
              else
          {
                    if($result)
            {
                return "OK";
            }
                else
            {
                return "NO";
            }
          }
    }
}
?>