PHP+MYSQL实例：网站在线人数的程序代码

<?php
//Put your basic server info here
$server = "localhost"; //normally localhost
$db_user = "root"; //your MySQL database username
$db_pass = "password"; //your MySQL database password
$database = "users";
$timeoutseconds = 300; //it will delete all people which haven't refreshed(so probbably are
// offline or inactive) in $timieoutseconds time (so it actually checks the people that are active in the last
// $timeoutseconds seconds)
//this is where PHP gets the time
$timestamp = time();
//counts the timeout, all people which have been seen last online in earlier than this timestamp, will get removed
$timeout = $timestamp-$timeoutseconds;
//connect to database
mysql_connect($server, $db_user);
//add the timestamp from the user to the online list
$insert = mysql_db_query($database, "INSERT INTO useronline VALUES
('$timestamp','".$_SERVER['REMOTE_ADDR']."','".$_SERVER['PHP_SELF']."')");
if(!($insert)) {
print "Useronline Insert Failed > ";
}
//delete the peoples which haven't been online/active in the last $timeoutseconds seconds.
$delete = mysql_db_query($database, "DELETE FROM useronline WHERE timestamp<$timeout");
if(!($delete)) {
print "Useronline Delete Failed > ";
}
//select the amount of people online, all uniques, which are online on THIS page
$result = mysql_db_query($database, "SELECT DISTINCT ip FROM useronline WHERE file='".$_SERVER['PHP_SELF']."' ");
if(!($result)) {
print "Useronline Select Error > ";
}
//Count the number of rows = the number of people online
$user = mysql_num_rows($result);
//spit out the results
mysql_close();
if($user == 1) {
print("1 user online\n");
} else {
print("$user users online\n");
}
?>