How to implement time limit in php

How to implement time limit in php: 1. Let the program execute without limit through "set_time_limit(0)"; 2. Set the memory limit through ini_set; 3. Set it to run every half hour.

The operating environment of this article: Windows7 system, PHP7.1 version, DELL G3 computer

How to achieve time limit in php?

Five ways to implement scheduled tasks in PHP

In the past few days, I need to use PHP to write a server application that regularly crawls web pages. I searched the Internet for solutions and found several solutions, which are summarized as follows.

Scheduled running tasks are a relatively important task for a website, such as regularly publishing documents, regularly cleaning up junk information, etc. Most of today’s websites use PHP dynamic language Developed, and the implementation of PHP determines that it does not have the concept of AppServer such as Java and .Net, and the http protocol is a stateless protocol. PHP can only be triggered and called by the user. After the call, it will automatically exit the memory. There is no Resident in memory.

If you have to use PHP to implement scheduled tasks, you can have the following solutions:

1. Simple, direct and reckless type

<?php
ignore_user_abort();//关掉浏览器，PHP脚本也可以继续执行.
set_time_limit(0);// 通过set_time_limit(0)可以让程序无限制的执行下去
ini_set(&#39;memory_limit&#39;,&#39;512M&#39;); // 设置内存限制
$interval=60*30;// 每隔半小时运行
do{
  //ToDo 
  sleep($interval);// 等待5分钟
}
while(true);

Disadvantages: After starting, it cannot Control, unless you terminate the PHP host. Do not use this method unless you are a hacker.

2. Simple and controllable

config.php

<?php
return 1;
?>

cron.php

ignore_user_abort();//关掉浏览器，PHP脚本也可以继续执行.
set_time_limit(0);// 通过set_time_limit(0)可以让程序无限制的执行下去
$interval=60*30;// 每隔半小时运行
do{
  $run = include 'config.php';
  if(!$run) die('process abort');
   
  //ToDo
  sleep($interval);// 等待5分钟
}
while(true);

Stop the program by changing return 0 in config.php. A feasible way is config. The php file interacts with a special form and is configured by setting some variables on the HTML page.

Disadvantages: It takes up system resources and runs for a long time, which may cause some unexpected hidden dangers. For example, memory management issues.

3. Simple improved

<?php
$time=15;
$url="http://".$_SERVER[&#39;HTTP_HOST&#39;].$_SERVER[&#39;REQUEST_URI&#39;];
/*
  function
*/
sleep($time);
file_get_contents($url);
?>

php script sleep continues to execute by accessing itself after a period of time. Just like a relay race.. This can ensure The execution time of each PHP script will not be too long. Therefore, it is not restricted by time_out.

Because each cycle of the php file is executed independently, this method avoids the restriction of time_out. However, It is best to add the control code. cofig.php as above, so that the process can be terminated.

4. Server scheduled tasks

Unix platform

If you use a Unix system, You need to add a special line of code at the beginning of your PHP script to enable it to be executed, so that the system knows what program to use to run the script. The first line of code added for Unix systems will not affect the running of the script under Windows, so you can also use this method to write cross-platform scripts.

1. Use PHP to execute the script in Crontab

Just like calling an ordinary shell script in Crontab (specific Crontab usage), use the PHP program to call the PHP script and execute it every hour myscript.php is as follows:

# crontab -e
00 * * * * /usr/local/bin/php /home/john/myscript.php

/usr/local/bin/php is the path of the PHP program.

2. Use URL to execute scripts in Crontab

If your PHP script can be triggered by URL, you can use lynx or curl or wget to configure your Crontab.

The following example uses a Lynx text browser to access a URL to execute a PHP script every hour. Lynx text browser uses conversational mode to open URLs by default. However, as shown below, we use the -dump option on the lynx command line to convert the URL output to standard output.

00 * * * * lynx -dump http://www.sf.net/myscript.php

The following example uses CURL to access the URL to execute a PHP script every 5 minutes. Curl displays output on standard output by default. Using the "curl -o" option, you can also dump the output of the script to a temporary file temp.txt.

*/5 * * * * /usr/bin/curl -o temp.txt http://www.sf.net/myscript.php

The following example uses WGET to access the URL to execute a PHP script every 10 minutes. The -q option indicates quiet mode. "-O temp.txt" means output will be sent to a temporary file.

*/10 * * * * /usr/bin/wget -q -O temp.txt http://www.sf.net/myscript.php

5. Detailed explanation of ini_set function usage

PHP ini_set is used to set the value of php.ini. It takes effect when the function is executed. After the script ends, the setting becomes invalid. You can modify the configuration without opening the php.ini file, which is very convenient for virtual spaces.

Function format:

string ini_set(string $varname, string $newvalue)

Not all parameters can be configured, you can view the list in the manual.

Common settings:

@ ini_set('memory_limit', '64M');

menory_limit: Set the maximum number of memory bytes that a script can apply for, which helps poorly written scripts consume the available memory on the server. The @ symbol means no errors are output.

@ini_set('display_errors', 1);

display_errors: Set the category of error messages.

@ini_set('session.auto_start', 0);

session.auto_start: Whether to automatically open session processing. When set to 1, you do not need to manually open the session with session_start() in the program. You can also use session.

If the parameter is 0, there is no If you open the session manually, an error will be reported.

@ini_set('session.cache_expire', 180);

session.cache_expire: Specifies the limited period (minutes) of the session page in the client cache. The default is 180 minutes. If session.cache_limiter=nocache is set, the setting here is invalid.

@ini_set('session.use_cookies', 1);

session.use_cookies: Whether to use cookies to save the session ID on the client;

@ini_set('session.use_trans_sid', 0);

session.use_trans_sid: Whether to use clear code to display the SID (session ID) in the URL,

The default is disabled because it will bring security risks to your users:

Users may tell others the URL containing a valid sid through email/irc/QQ/MSN, etc.

URLs containing valid SIDs may be saved on public computers.

Users may save URLs with fixed SIDs in their favorites or browsing history. URL-based session management always carries more risks than cookie-based session management and should be disabled.

PHP scheduled tasks are a very interesting thing. The above are some of the solutions provided in this article. You can also develop your own solution through the ideas of this article. Hope it helps everyone in need.

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