代码

首先是创建MYSQL数据库表。

CREATE TABLE tablename (
field type(max_length) DEFAULT default_value (NOT) NULL
}

可以使用的SQL语句。

CREATE TABLE useronline (
timestamp int(15) DEFAULT 0 NOT NULL,
ip varchar(40) NOT NULL,
file varchar(100) NOT NULL,
PRIMARY KEY (timestamp),
KEY ip (ip),
KEY file (file)
);

下面我们开始使用PHP脚本，首先定义MYSQL的信息。

= "localhost"; //你的服务器
= "root"; //你的mysql的用户名
= "password"; //你的mysql的密码
= "users"; //表的名字

设置统计的时间(多少秒内在线人数)

= 300;

取当前时间。

= time();

上面的完整代码：

= "localhost"; //your server
= "root"; //your mysql database username
= "password"; //your mysql database password if any
= "users"; //the db name
= 300;//timeoutseconds limit
//get the current time
= time();
//calculate the lowest timestamp allowed
= -;
?>

连接mysql

mysql_connect(localhost, username, password);

也允许使用变量形式。

mysql_connect(, , );

如果mysql数据库没有密码的话可以使用下面代码连接（当然建议大家一定要设置好自己的密码，这样起码黑客得要解密啊）

mysql_connect(, );

查询数据库的代码：

mysql_db_query(database, query);

我们只要有访客就要增加一条记录。

= mysql_db_query(, "INSERT INTO useronline VALUES
(,".125.41.223.242.","./jiaocheng/sc.php.")");

然后我们给出如果用户用错误信息的处理方式。

if(!()) {
print "Useronline Insert Failed > ";
}

然后我们得实现当超过我们设置的时间我们就要删除该用户记录。

= mysql_db_query(, "DELETE FROM useronline WHERE timestamp<");

同样给出删除记录出错的处理。

if(!()) {
print "Useronline Delete Failed > ";
}

下面我们显示数据库中有多少个不同的IP

= mysql_db_query(, "SELECT DISTINCT ip FROM useronline WHERE file="./jiaocheng/sc.php." ");

我们使用mysql_num_rows(query);来统计用户，代码如下:

= mysql_num_rows();

最后我们要关闭数据库。

mysql_close();

显示在线的人数。

if( == 1) {
print("1 user onlinen");
} else {
print(" users onlinen");
}

最终把上面代码写成一个PHP文件如下。

//Put your basic server info here
= "localhost"; //normally localhost
= "root"; //your MySQL database username
= "password"; //your MySQL database password
= "users";
= 300; //it will delete all people which havent refreshed(so probbably are
// offline or inactive) in time (so it actually checks the people that are active in the last
// seconds)
//this is where PHP gets the time
= time();
//counts the timeout, all people which have been seen last online in earlier than this timestamp, will get removed
= -;
//connect to database
mysql_connect(, );
//add the timestamp from the user to the online list
= mysql_db_query(, "INSERT INTO useronline VALUES
(,".125.41.223.242.","./jiaocheng/sc.php.")");
if(!()) {
print "Useronline Insert Failed > ";
}
//delete the peoples which havent been online/active in the last seconds.
= mysql_db_query(, "DELETE FROM useronline WHERE timestamp<");
if(!()) {
print "Useronline Delete Failed > ";
}
//select the amount of people online, all uniques, which are online on THIS page
= mysql_db_query(, "SELECT DISTINCT ip FROM useronline WHERE file="./jiaocheng/sc.php." ");
if(!()) {
print "Useronline Select Error > ";
}
//Count the number of rows = the number of people online
= mysql_num_rows();
//spit out the results
mysql_close();
if( == 1) {
print("1 user onlinen");
} else {
print(" users onlinen");
}
?>