1 <?php
 2 class link_mysql{
 3     //1.declear the variable.but without assignment sentence
 4     //2.assignment sentence can only occur in a function body.
 5     //3.'website' is a default db,you can switch db use function switch_db;
 6     //4.to call a function a variable in class,you should use 'this' pointer.
 7     private $host,$uid,$pwd,$db,$link;
 8    
 9     public function __construct($host,$uid,$pwd,$db){
10         $this->host = $host;
11         $this->uid=$uid;
12         $this->pwd = $pwd;
13         $this->db=$db;
14         $this->link = mysql_connect($this->host,$this->uid,$this->pwd) or 
15         die('Not connect to mysql '.mysql_error());
16         $this->switch_db($this->db);
17         mysql_query('set names utf8');
18     }
19     //切换数据库的，所以脱离于构造函数
20     public function switch_db($db){
21         mysql_select_db($db,$this->link);
22     }
23     //执行sql语句
24     public function sql_query($sql){
25         $res = mysql_query($sql,$this->link);
26         $this->check_res($res);
27         return $res;
28     }
29     //取得结果数目
30     public function get_nums($tb){
31         $res = mysql_query("select count(*) as num from ".$tb);
32         $this->check_res($res);
33         $count_arr = mysql_fetch_array($res);
34         return $count_arr[0];
35     }
36     //取得多行多列的结果,得到一个二维数组
37     public function get_all($sql){
38         $res = mysql_query($sql,$this->link);
39         $this->check_res($res);
40         $arr = array();
41         while($row = mysql_fetch_assoc($res)){
42             $arr[] = $row;
43         }
44         return $arr;
45     }
46     //取得单行的结果，取得单行结果
47     public function get_row($sql){
48         $res = mysql_query($sql,$this->link);
49         $this->check_res($res);
50         $row = mysql_fetch_assoc($res);
51         return $row;  
52     }
53     //取得单个结果，一个字符串,由于我门不知道索引值，所以只能用mysql_fetch_array
54     public function get_one($sql){
55         $res = mysql_query($sql,$this->link);
56         $this->check_res($res);
57         $row = mysql_fetch_array($res);
58         return $row[0];
59     }
60     //检查资源是否为空
61     private function check_res($res){
62         if($res){
63             return false;
64         }
65     }
66     //析构函数
67     public function __destruct(){
68         mysql_close($this->link);
69     }
70     
71 }
72 
73 $link = new link_mysql('hostname','username','password','dbname');
74 $count = $link->get_nums('tablename');
75 echo 'The nums of table **** is :'.$count;
76 unset($link);
77 ?>