PHP realizes the function of accurately counting the number of people online

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 also distinguish visitors. 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 that several of the above functions have parameters passed in. , you just need to indicate that there is an incoming transmission. 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.

Note: Any time 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 that can be linked

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. What is 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 have parameters 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 operated for 10 minutes will be cleared.

The code for accurately realizing the method of counting the number of online people through PHP:

<?php
$filename=&#39;online.txt&#39;;//数据文件
$cookiename=&#39;VGOTCN_OnLineCount&#39;;//cookie名称
$onlinetime=600;//在线有效时间，单位：秒 (即600等于10分钟)
   
$online=file($filename);
//PHP file() 函数把整个文件读入一个数组中。与 file_get_contents() 类似，不同的是 file() 将文件作为一个数组返回。数组中的每个单元都是文件中相应的一行，包括换行符在内。如果失败，则返回 false
$nowtime=$_SERVER[&#39;REQUEST_TIME&#39;];
$nowonline=array();
//得到仍然有效的数据
foreach($online as $line){
  $row=explode(&#39;|&#39;,$line);
  $sesstime=trim($row[1]);
  if(($nowtime - $sesstime)<=$onlinetime){//如果仍在有效时间内，则数据继续保存，否则被放弃不再统计
    $nowonline[$row[0]]=$sesstime;//获取在线列表到数组，会话ID为键名，最后通信时间为键值
  }
}
/*
@创建访问者通信状态
使用cookie通信
COOKIE 将在关闭浏览器时失效，但如果不关闭浏览器，此 COOKIE 将一直有效，直到程序设置的在线时间超时
*/
if(isset($_COOKIE[$cookiename])){//如果有COOKIE即并非初次访问则不添加人数并更新通信时间
  $uid=$_COOKIE[$cookiename];
}else{//如果没有COOKIE即是初次访问
  $vid=0;//初始化访问者ID
  do{//给用户一个新ID
    $vid++;
    $uid=&#39;U&#39;.$vid;
  }while(array_key_exists($uid,$nowonline));
  setcookie($cookiename,$uid);
}
$nowonline[$uid]=$nowtime;//更新现在的时间状态
//统计现在在线人数
$total_online=count($nowonline);
//写入数据
if($fp=@fopen($filename,&#39;w&#39;)){
  if(flock($fp,LOCK_EX)){
    rewind($fp);
    foreach($nowonline as $fuid=>$ftime){
      $fline=$fuid.&#39;|&#39;.$ftime."\n";
      @fputs($fp,$fline);
    }
    flock($fp,LOCK_UN);
    fclose($fp);
  }
}
echo &#39;document.write("&#39;.$total_online.&#39;");&#39;;

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