PHP implements scheduled tasks and continuous process examples fsockopen

The web server executes a PHP script, and sometimes it takes a long time to return the execution results, and subsequent scripts need to wait for a long time before they can continue to execute. If you want to simply trigger the execution of a time-consuming script without waiting for the execution result and then directly perform the next operation, you can use the fscokopen function to achieve this.

PHP supports socket programming. The fscokopen function returns a handle to the remote host connection. You can perform fwrite, fgets, fread and other operations on it just like using the handle returned by fopen. Use fsockopen to connect to the local server, trigger script execution, and then return immediately without waiting for the script execution to complete, thereby achieving the effect of asynchronous PHP execution.

<?
function triggerRequest($url, $post_data = array(), $cookie = array()){
        $method = "GET";  //通过POST或者GET传递一些参数给要触发的脚本
        $url_array = parse_url($url); //获取URL信息
        $port = isset($url_array[&#39;port&#39;])? $url_array[&#39;port&#39;] : 80;  
        $fp = fsockopen($url_array[&#39;host&#39;], $port, $errno, $errstr, 30);
        if (!$fp) {
                return FALSE;
        }
        $getPath = $url_array[&#39;path&#39;] ."?". $url_array[&#39;query&#39;];
        if(!empty($post_data)){
                $method = "POST";
        }
        $header = $method . " " . $getPath;
        $header .= " HTTP/1.1\r\n";
        $header .= "Host: ". $url_array[&#39;host&#39;] . "\r\n "; //HTTP 1.1 Host域不能省略
        /*以下头信息域可以省略
        $header .= "User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.13) Gecko/20080311 Firefox/2.0.0.13 \r\n";
        $header .= "Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,q=0.5 \r\n";
        $header .= "Accept-Language: en-us,en;q=0.5 ";
        $header .= "Accept-Encoding: gzip,deflate\r\n";
         */
        $header .= "Connection:Close\r\n";
        if(!empty($cookie)){
                $_cookie = strval(NULL);
                foreach($cookie as $k => $v){
                        $_cookie .= $k."=".$v."; ";
                }
                $cookie_str =  "Cookie: " . base64_encode($_cookie) ." \r\n"; //传递Cookie
                $header .= $cookie_str;
        }
        if(!empty($post_data)){
                $_post = strval(NULL);
                foreach($post_data as $k => $v){
                        $_post .= $k."=".$v."&";
                }
                $post_str  = "Content-Type: application/x-www-form-urlencoded\r\n"; 
                $post_str .= "Content-Length: ". strlen($_post) ." \r\n"; //POST数据的长度
                $post_str .= $_post."\r\n\r\n "; //传递POST数据
                $header .= $post_str;
        }
        fwrite($fp, $header);
        //echo fread($fp, 1024); //服务器返回
        fclose($fp);
        return true;
}

In this way, the execution of a PHP script can be triggered through the fsockopen() function, and then the function will return. Then proceed to the next step.
There is a problem now: when the client disconnects, that is, after triggerRequest sends the request, the connection is closed immediately, which may cause the script being executed on the server to exit

Inside PHP, the system maintains the connection status, and other There are three possible statuses:
* 0 – NORMAL (normal)
* 1 – ABORTED (abnormal exit)
* 2 – TIMEOUT (timeout)
When the PHP script runs normally in the NORMAL state, the connection is valid. When the client disconnects, the ABORTED status flag will be turned on. Interruption of the remote client connection is usually caused by the user clicking the STOP button. When the connection time exceeds PHP's time limit (see set_time_limit() function), the TIMEOUT status flag will be turned on.

You can decide whether the script needs to exit when the client disconnects. Sometimes it is convenient to have a script run completely, even if no remote browser accepts the script's output. The default is that the script will exit when the remote client connection is interrupted. This processing can be controlled by ignore_user_abort in php.ini or by the corresponding "php_value ignore_user_abort" and ignore_user_abort() functions in the Apache .conf settings. If PHP is not told to ignore user interruptions, the script will be interrupted, unless register_shutdown_function() allows us to set another function that can be called when execution is shut down. This means that when our script completes execution or dies unexpectedly When the PHP execution is about to be shut down, our function will be called. When the remote user clicks the STOP button and the script tries to output data again, PHP will detect that the connection has been interrupted and call the shutdown trigger function.
　Scripts may also be interrupted by the built-in script timer. The default timeout limit is 30 seconds. This value can be changed by setting max_execution_time in php.ini or the corresponding "php_value max_execution_time" parameter in the Apache .conf settings or the set_time_limit() function. When the counter times out, the script will exit similar to the above connection interruption situation, and the previously registered shutdown trigger function will also be executed at this time. In the shutdown trigger function, you can check whether the timeout caused the shutdown trigger function to be called by calling the connection_status() function. If a timeout results in a call to the shutdown triggering function, the function will return 2.
　One thing to note is that the ABORTED and TIMEOUT states can be valid at the same time. This is possible when telling PHP to ignore user exit actions. PHP will still notice that the user has disconnected but the script is still running. If the running time limit is reached, the script will be exited and the set shutdown trigger function will also be executed. At this point you will find that the function connection_status() returns 3.
So also specify in the script to be triggered:

<?php  
　　ignore_user_abort(TRUE); //如果客户端断开连接，不会引起脚本abort  
　　set_time_limit(0); //取消脚本执行延时上限

or use:

<?php  
　　register_shutdown_function(callback fuction[, parameters]); //注册脚本退出时执行的函数