<?php

class Test{

    public $a=1;

    protected $b=2;

    private $c=3;

    public function fun1(){

        //echo "fun1";

        //调用fun2

        $this->b=789;

        $this->fun2();

        //echo $this->c;

    }

    protected function fun2(){

        //echo "fun2";

        echo $this->b;

    }

    private function fun3(){

        echo "fun3";

    }

}

require 'Test.class.php';

$ob=new Test();

echo $ob->a;

echo "<hr/>";

$ob->fun1();

class Person{

     function __construct($name,$sex)

     {

          $this->name=$name;

          $this->sex=$sex;

     }                                              //定义类的属性

     function showName()

     {

         echo $this->name;              //定义类的showName方法

     }

     function showSex()

    {

         echo $this->sex;                 //定义类的showSex方法

    }

 }

 class Worker extends Person{

     function __construct($name,$sex,$job)

     {

           parent::__construct($name,$sex);   //调用Person构造                           函数，继承Person

     }

 }

<?php

class DB{

    protected $conn="";

    /*

     * 作用：连接数据库，打开 设置交互字符集，选择数据库

     * 参数：host  username  password dbName charset

     * 返回值：bool

     */

    function connect($host,$username,$password,$dbName,$charset='utf8'){

        $link=mysql_connect($host,$username,$password);

        $this->conn=$link;

        if(is_resource($link)){

            mysql_set_charset($charset);

            $re=mysql_select_db($dbName);

            if($re){

                return true;

            }else{

                return false;

            }

        }else{

            return false;

        }

    }

    /*

     * 作用：执行sql语句

     * 参数：sql语句

     * 返回值：update delete 返回影响记录条数

     *          insert 返回主键id值

     *          select 返回二维数组

     */

    function query($sql){

        $re=mysql_query($sql);

        if($re){

            //判断sql语句的类型

            if(preg_match("/^update|^delete/i",$sql)){

                return mysql_affected_rows();

            }else if(preg_match("/^insert/i",$sql)){

                return mysql_insert_id();

            }else if(preg_match("/^select/i",$sql)){

                //返回二维数组

                $arr=array();

                while($row=mysql_fetch_assoc($re)){

                    $arr[]=$row;

                }

                return $arr;

            }else{

                return $re;

            }

        }else{

            return false;

        }

    }

    /*

     * 作用：关闭数据库连接

     * return:bool

     */

    function close(){

        return mysql_close($this->conn);

    }

}

<?php

header("content-type:text/html;charset=utf-8");

require 'Db.class.php';

$ob=new Db();

$ob->connect("localhost", 'root', 'root', 'cms');

$arr=$ob->query("select * from news limit 5");

var_dump($arr);

$ob->close();