mysql简单类

刚刚学习类，写了一个简单的mysql类。试着调用这个类后，终于对类和oop有些新的认识。

db_mysql.php
class db_mysql{
        var $Host = HOST;
        var $User = USER;
        var $Password = PASS;
        var $Database = DATABASE;

        var $Link_ID = null;
        var $Query_ID = null;
        var $Result = null;
        var $sql = null;

        function db_mysql(){
                global $HOST;
                global $USER;
                global $PASS;
                global $DATABASE;
                $this->Host = $HOST;
                $this->User = $USER;
                $this->Password = $PASS;
                $this->Database = $DATABASE;
        }

        function link_id() {
                return $this->Link_ID;
        }

        function query_id() {
                return $this->Query_ID;
        }

        function connect() {
                $this->Link_ID = mysql_connect($this->Host,$this->User,$this->Password);
                return $this->Link_ID;
        }

        function select_db() {
                if ($this->Link_ID) {
                        mysql_select_db($this->Database);
                }
        }

        function query($sql) {
                $this->sql = $sql;
                $this->Result = mysql_query($this->sql,$this->Link_ID);
                return $this->Result;
        }

        function insert($sql) {
                $this->sql = $sql;
                $this->Result = mysql_query($this->sql,$this->Link_ID);
                return $this->Result;
        }

        function update($sql) {
                $this->sql = $sql;
                $this->Result = mysql_query($this->sql,$this->Link_ID);
                return $this->Result;
        }

        function delete($sql) {
                $this->sql = $sql;
                $this->Result = mysql_query($this->sql,$this->Link_ID);
                return $this->Result;
        }



        function free() {
                if ($this->Query_ID) {
                        @mysql_free_result($this->Query_ID);
                        $this->Query_ID = 0;
                }
        }

        function Close(){
                if ($this->Link_ID) {
                        mysql_close($this->Link_ID);
                }
                else {
                        @mysql_close($this->Link_ID);
                }
        }
}
?>

调用类的例子：
include("db_mysql.php"); //引入类
$mysql = new db_mysql;   //初始化对象
$mysql->connect();      //调用方法
if ($mysql->Link_ID) {
  echo "success";
}else{
  echo "fail";
}
?>