Comparison of several methods of implementing timed tasks in PHP

Several methods of implementing timed tasks in PHP

These days need to use PHP to write a timed crawl Web server application. Search on the Internet for a solution, found Oschina a question of the answer is wonderful

Several solutions are proposed.

I. Simple direct disregard of the consequences type

Ignore_user_abort ();//switch off the browser, the PHP script can also continue to execute. Set_time_limit (0);//Through Set_time_limit (0) You can allow the program to execute indefinitely $interval=60*30;/ /Run do{    //todo      sleep ($interval) every half hour;//wait 5 minutes}while (true);

Disadvantage: After booting, you cannot control it unless you terminate the PHP host. Do not use this method unless you are a hacker.

Two. Simple and controllable type

config.php

return 1;
 
  

cron.php

Ignore_user_abort ();//switch off the browser, the PHP script can also continue to execute. Set_time_limit (0);//Through Set_time_limit (0) You can allow the program to execute indefinitely $interval=60*30;/ /Every half hour run do{$run = include ' config.php ', if (! $run) die (' Process abort ');//todo  Sleep ($interval);//wait 5 minutes}while ( true);

The STOP program is implemented by changing the return 0 of the config.php. One way to do this is to config.php a file with a special form and set some variables to configure it via HTML pages.

Disadvantages: Accounting for system resources, long-running, there will be some unexpected hidden dangers. For example, memory management problems.

Three. Simple and improved type

$time =15; $url = "http://". $_server[' http_host '].$_server[' Request_uri '];/*    function*/sleep ($time); file_get_ Contents ($url);

The PHP script continues to execute after a period of time by accessing itself. It's like a relay race. This guarantees that each PHP script will not take too long to execute. It is not subject to time_out restrictions.

Because each time the PHP file is executed independently, this method avoids the time_out limitation. But it's best to add the control code to the top. Cofig.php so that the process can be terminated.

Four. CronTab type

Ccontroljobnum (1); while (true) {         
 
           
  
   <动态sleep>
    
                            } function Ccontroljobnum ($job _limit) {                 $cmd = @popen ("Ps-ef | grep ' {$_server[' script_filename '} ' | Grep-v grep | Wc-l ", ' R ');                 $num = @fread ($cmd, up to);                 $num + = 0;                 @pclose ($cmd);                 if ($num > $job _limit)                 {                         exit;                 }                 return true; }
  
   
 
  

The number of running processes is determined by Popen in the program to control concurrency

Five. Use the Cron service on BAE or SAE.

Six. Buy a VPS, with crontab

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