How does phg count the number of people online?

This article mainly introduces the function of counting the number of online people in PHP, and analyzes the related operation skills of PHP based on session object calculation and counting the number of online people in the form of examples. Friends in need can refer to the following

The examples of this article are described Developed PHP method to count the number of people online. Share it with everyone for your reference, the details are as follows:

I remember that in ASP, you can use the application object to count the number of people online. How to design PHP?

PHP encapsulates the session object very well. According to the HTTP protocol, visitors to each range of websites can generate a unique identifier

echo session_id();
//6ed364143f076d136f404ed93c034201<br />

This is the key to counting the number of people online. Only with this session_id can we distinguish the people visiting. Because everyone is different.
Next, how to store the value in the session variable into the database. Here we will introduce another function

bool session_set_save_handler ( callable $open , callable $close , callable $read , callable $write , callable$destroy , callable $gc )
//callable 可随时支取的，请求即付的，随时可偿还的
// open(string $savePath, string $sessionName) 打开连接
//close() 关闭连接
//read(string $sessionId) 对出数据
//write(string $sessionId, string $data) //写入数据
//destroy($sessionId) //删除数据
//gc($lifetime) //垃圾回收函数

Note, several functions above have parameters Incoming, you just need to indicate that there is a transfer incoming. When PHP executes the code, it will automatically read the parameters in

session

The next step is to complete the above five functions and a main function

session_set_save_handler(
   array("session","open"),
   array("session","close"),
   array("session","read"),
   array("session","write"),
   array("session","destroy"),
   array("session","gc")
);

The main function is completed in this way, but why do you need to use array("session", "method") to call these methods? I really don't understand

(Basically understand: Whenever you pass an object's method as a parameter, you need to use this form: array(object, "method name"))

The next step is to write each function

//链接数据的open
function open($path,$sessname) {
  $db = mysql_connect("localhost","root","123456","test");
  mysql_select_db("test",$db);
  mysql_query("SET NAMES UTF8");
  return true;
}

Close The data can be linked close

function close(){
$db = mysql_connect("localhost","root","123456","test");
mysql_close($db);
return true;
}

The key function is about to start, display the reading function read(), mainly, the read() function has a value passed in, and the passed in is session_id

function read($sid){
  $sql = "select data from session where sid='{$sid}' and card='".self::$card."'";
  $query = mysql_query($sql) or die(mysql_error());
  $row = mysql_fetch_array($query);
  $row>0?$row["data"]:" ";
}

The second is the write function. If the data exists in the database, just update the time and write the new data

function write($sid,$data)
{
   $sql = "select sid from session where sid='{$sid}' and card='".self::$card."'";
   $query = mysql_query($sql) or die(mysql_error());
   $mtime = time();
   $num = mysql_num_rows($query);
   if($num){
    $sql = "UPDATE session SET data='{$data}', mtime ='{$mtime}'";
   }else{
    $sql = "INSERT INTO session (sid,data,mtime,ip,card) VALUES('{$sid}','{$data}','".time()."','{$_SERVER['REMOTE_ADDR']}','".self::$card."')";
   }
   mysql_query($sql);
   return true;
}

The next step is the function that embodies the PHP recycling mechanism. Both functions are included. Parameters are passed in.

function destroy($sid){
  $sql = "DELETE FROM session WHERE sid='{$sid}'";
  mysql_query($sql) or die(mysql_error());
  return true;
}
function gc($max_time){
  $max_time = 600;
  $sql = "DELETE FROM session WHERE `mtime`<&#39;".(time()-$max_time)."&#39;";
  mysql_query($sql) or die(mysql_error());
  return true;
}

Okay, the five functions are completed, and then the number of session records is read out from the session table. You can accurately count the number of people visiting the page.

User records that have not been operated for 10 minutes will be cleared

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