支持php4、php5的mysql数据库操作类

    * @param string $password
    * @param string $database
    */
   function __construct($host="localhost",$user="root",$password="",$database="")
   {
       $this->set("host",$host);
       $this->set("user",$user);
       $this->set("password",$password);
       $this->set("database",$database);
       $this->connect();
   }

   /**
    * set the value for the param of this class
    *
    * @param string $var
    * @param string $value
    */
   function set($var,$value)
   {
       $this->$var=$value;
   }

   
   /**
    * connect to a mysql server,and choose the database.
    *
    * @param string $database
    * @param string $host
    * @param string $user
    * @param string $password
    * @return link_id
    */
   function connect($database="",$host="",$user="",$password="")
   {
       if(!empty($database))$this->set("database",$database);
       if(!empty($host))$this->set("host",$host);
       if(!empty($user))$this->set("user",$user);
       if(!empty($password))$this->set("password",$password);
       if($this->link_id==0)
       {
           if($this->pconnect)
              $this->link_id=@mysql_pconnect($this->host,$this->user,$this->password);
           else 
              $this->link_id=@mysql_connect($this->host,$this->user,$this->password);
           if(!$this->link_id)
              die("Mysql Connect Error in ".__FUNCTION__."():".mysql_errno().":".mysql_error());