Detailed explanation of how to implement scheduled tasks in PHP_PHP Tutorial

I analyzed in uchome, this is how uchome does it
1. Store all scheduled tasks in the database
2. Every time the user performs an operation or opens the page, Execute a planned task in order. That is to say, it is judged in turn. When the time is up, it will be executed in the user process.
The planned task code of uchome is in ./source/function_cron.php
Only analyze the uchome code by yourself about the plan The approximate results of the task, just to inspire others. I hope someone has a good method to share.
ignore_user_abort()
I have thoroughly studied planned tasks some time ago and think that there are many ideas for planned tasks, but the most suitable for the Web is triggering The formula is similar to DZ and PHPWind. It seems that most web applications also do this. Here are a few other ones for reference
1. In order to provide stable triggering, use crontab+wget or ab to provide scheduled access.
2. Nohup + PHP writing daemon
3. Directly use PHP to write an infinite loop and provide triggering. At this time, you need to use cache or database to assist in launching the loop, and you must use sleep or usleep to control the trigger frequency
4, crontab+php
5, web triggering methods, there are also differences, one is timing triggering, the other is periodic triggering, DZ and PHPWind are both timing triggering, I finally used periodic triggering
The specific implementation idea is easy to think of, so I won’t go into details.
If you have a host, you must use crontab to execute the command line PHP. If you use a loop, it is best to separate the loop from the specific processing program, otherwise the memory will keep increasing.

I accidentally discovered this function -ignore_user_abort in the PHP manual today. This function can help us implement scheduled tasks like cron in Linux. Let's take a look at how to implement it.

First look at the explanation of this function in the php manual

Description

int ignore_user_abort ([ bool $setting ] )

Sets whether a client disconnect should cause a script to be aborted.

That is to say, no matter whether the client closes the browser or not, the following program will be executed.

Let’s take a look at its parameters

Parameters

setting

If not set, the function will only return the current setting.

This function accepts a parameter to determine whether to enable the ignore_user_abort function.

Look at the return value:

Return Values

Returns the previous setting, as a boolean.

It says here that the previous setting is returned, and it is a bool value. After my testing, this statement is wrong. The returned value is obviously int type. If you don’t believe it, you can write a php file to test it.

Having said so much, how to use this function in PHP to implement scheduled tasks? Also, with the help of another function, this function is set_time_limit. Through set_time_limit0), you can set the running time of the program to be unlimited. The default running time of PHP is 30 seconds. Through set_time_limit(0), the program can be executed without limit. Just add ignore_user_abort (1) and set_time_limit (0) before the program is executed. How to write the final program? Let me give you an example.

ignore_user_abort(); // run script in background
set_time_limit(0); // run script forever
$interval=30; // do every 15 minutes…
do{
$fp = fopen('text3.txt','a') ;
fwrite($fp,'test');
fclose($fp);
sleep($interval); // wait 15 minutes
}while(true);
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