PHP server-side multi-process programming practice_PHP tutorial

I recently compared the features of PHP with Python and Erlang, and found that PHP has many features that people don’t often use. Many great applications can be implemented using the PHP CLI. For example, search engine crawlers and long-running calculation scripts can completely replace other languages ​​for server operation and maintenance. This is even more powerful for those familiar with PHP.

Why is multi-processing in PHP good? The reason why most online game servers use multi-threading instead of multi-process is that processes are more stable than threads. Moreover, multi-threading is suitable for the application scenarios of current multi-core servers and can better utilize the capabilities of multi-core computing. Process maintenance can use many operating system level tools. Message Queue solves many thread communication problems. Therefore, PHP multi-process is very suitable for server-side computing-intensive applications.

According to a Vietnamese IT company, they have successfully used PHP background multi-process in enterprise-level applications such as the distribution of legal documents and processing bank account amounts.

Using the background PHP process can process web page requests at the same time without affecting the server. Once this kind of background process fails, it is easy to find out the cause and restore or remedy it, so it is more robust. Different processes are isolated from each other, more efficient, and each service process can be scheduled uniformly.

PHP is currently the most widely used web development language, so using PHP for server-side applications can reduce costs. You can use existing personnel, existing configurations, and even code reuse. What kind of scenarios are more suitable for using PHP background multi-process? For example, email distribution, remote service invocation, data aggregation, scheduled tasks, and calculation result caching are places that do not need to be returned immediately.

PHP single process can completely achieve the goal in some places, and it is easier to implement. There is no need to consider the synchronization of the process or the sharing of data. PHP CLI (SAPI SERVER API) command line interface can be used to do CRON scheduled tasks and graphical interface programs (using GTK library).

PHP CLI Example

<ol class="dp-c">
<li class="alt"><span><span>php -f test.php    </span></span></li>
<li>
<span>php -r “</span><span class="func">echo</span><span> time();”    </span>
</li>
<li class="alt">
<span>php -R </span><span class="keyword">as</span><span> python style  </span>
</li>
</ol>

PHP reads command line parameters:

<ol class="dp-c"><li class="alt"><span><span><?php   </span></span></li><li><span>#!/usr/bin/php -q    </span></li><li class="alt"><span class="func">echo</span><span> &ldquo;Test Arguments:
&rdquo;;    </span></li><li><span class="func">echo</span><span> </span><span class="vars">$_SERVER</span><span>[</span><span class="string">"argc"</span><span>].&rdquo;
&rdquo;;    </span></li><li class="alt"><span class="func">echo</span><span> </span><span class="vars">$_SERVER</span><span>[</span><span class="string">"argv"</span><span>][0].&rdquo;
&rdquo;;    </span></li><li><span>?>  </span></span></li></ol>

PHP command line interface standard input and output:

<ol class="dp-c"><li class="alt"><span><span><?php   </span></span></li><li><span>#!/usr/bin/php -q    </span></li><li class="alt"><span class="comment">/* Define STDIN in case if it is not already defined by PHP for some reason */</span><span>    </span></li><li><span class="keyword">if</span><span>(!defined(&ldquo;STDIN&rdquo;)) {    </span></li><li class="alt"><span>define(&ldquo;STDIN&rdquo;, </span><span class="func">fopen</span><span>(&lsquo;php:</span><span class="comment">//stdin&rsquo;,r&rsquo;))   </span><span> </span></li><li><span>}    </span></li><li class="alt"><span>   </span></li><li><span class="func">echo</span><span> &ldquo;Hello! What is your name (enter below):
&rdquo;;    </span></li><li class="alt"><span class="vars">$strName</span><span> = </span><span class="func">fread</span><span>(STDIN, 80); </span><span class="comment">// Read up to 80 characters or a newline   </span><span> </span></li><li><span class="func">echo</span><span> &lsquo;Hello &lsquo; , </span><span class="vars">$strName</span><span> , &ldquo;
&rdquo;;    </span></li><li class="alt"><span>?>  </span></span></li></ol>

CRONJOB can run certain tasks regularly, but it must be prevented from running repeatedly. A lock file is created at the beginning and deleted at the end. Or use the ps command to process it. Task queue can be implemented using MySQL, or Key/VALUE database, or message queue.

Process control related functions:

<ol class="dp-xml">
<li class="alt"><span><span>Process Control Extensions    </span></span></li>
<li><span>pcntl_fork()    </span></li>
<li class="alt"><span>posix_setsid()    </span></li>
<li><span>posix_kill    </span></li>
<li class="alt"><span>pcntl_wait    </span></li>
<li><span>pcntl_signal    </span></li>
<li class="alt"><span>   </span></li>
<li><span>SIGHUP    </span></li>
<li class="alt"><span>SIGTERM; system shutdown, kill    </span></li>
<li><span>SIGINT; sent by Ctrl+c    </span></li>
<li class="alt"><span>SIGKILL (uncatchable); unresponsive, kill -9    </span></li>
<li><span>SIGCHLD; child status change    </span></li>
<li class="alt"><span>SIGSTP; sent by Ctrl+z    </span></li>
<li><span>SIGCONT; resume from stop, fg  </span></li>
</ol>

PHP cannot throw exceptions for certain errors. How to improve the fault tolerance of PHP multi-process applications?

　◆You can monitor the process and report when the dependent process fails.

　◆Use CRONJOB to monitor the process.

　◆Write the PID of the monitored process into a file.

　◆Check regularly whether the PID file exists. Check ps -o pid= or file_exists(‘/proc/’).

　◆If the thread does not exist, restart the process.

Looking back at the past, server-side services that were done in Java or Python can be implemented in PHP. A single language is easier to maintain. In the past, people's understanding of the Web language was very one-sided. Things such as multi-threading and transactions can be changed to achieve the same purpose.