An in-depth explanation of the types of PHP thread concurrency_PHP Tutorial

Threads are our first consideration when doing projects. How to implement threads in PHP? Here we will take a look at the implementation of PHP threads. Many PHP developers believe that multitasking is impossible for real PHP applications due to the lack of threading capabilities in standard PHP.

For example, if an application requires information from another Web site, it must be stopped until the remote retrieval is complete. This is wrong! Learn how to implement in-process PHP multitasking using stream_select and stream_socket_client in this article. PHP does not support threads. Nonetheless, contrary to what most PHP developers believe above, PHP applications can perform multitasking. Let’s start by describing as clearly as possible what “multitasking” and “threading” mean for PHP programming.

Types of PHP thread concurrency

First of all, let’s put aside a few examples that are irrelevant to the topic. PHP's relationship with multitasking or concurrency is complex. At a high level, PHP often involves multitasking: in a multitasking manner using a standard server-side PHP installation - for example, as an Apache module. In other words, several clients - Web browsers - can request the same PHP-interpreted page at the same time, and the Web server will return all of them at about the same time.

One web page will not block the delivery of other web pages, although they may slightly block each other due to constrained resources such as server memory or network bandwidth. Thus, system-level requirements for achieving concurrency may lend themselves to PHP-based solutions. In terms of implementation, PHP allows its managing web server to be responsible for implementing concurrency.

Client-side concurrency under the name of Ajax has also become the focus of developers in recent years. Although the meaning of Ajax has become quite vague, one aspect of it is that the browser display can simultaneously perform calculations and retain responses to user actions such as selecting menu items. This is actually some kind of multitasking. Ajax coded in PHP is just that - but it doesn't involve any specific PHP; Ajax frameworks for other languages ​​all operate in exactly the same way.

A third concurrency instance that only briefly touches on PHP is PHP/TK. PHP/TK is an extension to PHP that provides portable graphical user interface (GUI) bindings for core PHP. PHP/TK allows you to write code in PHP to construct desktop GUI applications. Its event-based nature will simulate a form of concurrency that is easy to master and less error-prone than threads. Furthermore, concurrency is "inherited" from an assistive technology rather than a fundamental feature of PHP.

There have been many experiments with adding threading support to PHP itself. As far as I know, none have been successful. However, the Ajax framework and PHP/TK's event-oriented implementation suggest that events may be a better representation of PHP's concurrency than threads. PHP V5 proves that this is indeed the case. With standard PHP V4 and lower, all work of a PHP application must be performed sequentially. For example, if a program needs to retrieve the price of an item at two business sites, it requests the price from the first site, waits until a response arrives, then requests the price from the second site, and then waits again. What happens if a program asks for several tasks to be completed simultaneously? Overall, the program will complete over a period of time, during which time continuous processing will always occur.

First example PHP thread The new stream_select function and several of its helpers make this possible. Consider the following example.

Listing 1. Requesting multiple HTTP pages simultaneously

<ol class="dp-xml">
<li class="alt"><span><span>＜?php  </span></span></li>
<li class=""><span>echo "Program starts at ". date('h:i:s') . ".n";  </span></li>
<li class="alt"><span> </span></li>
<li class="">
<span>$</span><span class="attribute">timeout</span><span>=</span><span class="attribute-value">10</span><span>;  </span>
</li>
<li class="alt">
<span>$</span><span class="attribute">result</span><span>=</span><span class="attribute-value">array</span><span>();  </span>
</li>
<li class="">
<span>$</span><span class="attribute">sockets</span><span>=</span><span class="attribute-value">array</span><span>();  </span>
</li>
<li class="alt">
<span>$</span><span class="attribute">convenient_read_block</span><span>=</span><span class="attribute-value">8192</span><span>;  </span>
</li>
<li class=""><span> </span></li>
<li class="alt"><span>/* Issue all requests simultaneously; there's no blocking. */  </span></li>
<li class="">
<span>$</span><span class="attribute">delay</span><span>=</span><span class="attribute-value">15</span><span>;  </span>
</li>
<li class="alt">
<span>$</span><span class="attribute">id</span><span>=</span><span class="attribute-value">0</span><span>;  </span>
</li>
<li class=""><span>while ($delay ＞ 0) {  </span></li>
<li class="alt">
<span>$</span><span class="attribute">s</span><span>=</span><span class="attribute-value">stream_socket_client</span><span>("phaseit.net:80", $errno,  </span>
</li>
<li class=""><span>$errstr, $timeout,  </span></li>
<li class="alt"><span>STREAM_CLIENT_ASYNC_CONNECT|STREAM_CLIENT_CONNECT);  </span></li>
<li class=""><span>if ($s) {  </span></li>
<li class="alt"><span>$sockets[$id++]=$s;  </span></li>
<li class="">
<span>$</span><span class="attribute">http_message</span><span>=</span><span class="attribute-value">"GET /demonstration/delay?delay="</span><span> .  </span>
</li>
<li class="alt"><span>$delay . " HTTP/1.0rnHost: phaseit.netrnrn";  </span></li>
<li class=""><span>fwrite($s, $http_message);  </span></li>
<li class="alt"><span>} else {  </span></li>
<li class=""><span>echo "Stream " . $id . " failed to open correctly.";  </span></li>
<li class="alt"><span>}  </span></li>
<li class="">
<span>$delay </span><span class="attribute">-</span><span>= </span><span class="attribute-value">3</span><span>;  </span>
</li>
<li class="alt"><span>}  </span></li>
<li class=""><span> </span></li>
<li class="alt"><span>while (count($sockets)) {  </span></li>
<li class="">
<span>$</span><span class="attribute">read</span><span>=$sockets;  </span>
</li>
<li class="alt">
<span>stream_select($read, $</span><span class="attribute">w</span><span>=</span><span class="attribute-value">null</span><span>, $</span><span class="attribute">e</span><span>=</span><span class="attribute-value">null</span><span>, $timeout);  </span>
</li>
<li class=""><span>if (count($read)) {  </span></li>
<li class="alt"><span>/* stream_select generally shuffles $read, so we need to  </span></li>
<li class=""><span>compute from which socket(s) we're reading. */  </span></li>
<li class="alt"><span>foreach ($read as $r) {  </span></li>
<li class="">
<span>$</span><span class="attribute">id</span><span>=</span><span class="attribute-value">array_search</span><span>($r, $sockets);  </span>
</li>
<li class="alt">
<span>$</span><span class="attribute">data</span><span>=</span><span class="attribute-value">fread</span><span>($r, $convenient_read_block);  </span>
</li>
<li class=""><span>/* A socket is readable either because it has  </span></li>
<li class="alt"><span>data to read, OR because it's at EOF. */  </span></li>
<li class=""><span>if (strlen($data) == 0) {  </span></li>
<li class="alt"><span>echo "Stream " . $id . " closes at " . date('h:i:s') . ".n";  </span></li>
<li class=""><span>fclose($r);  </span></li>
<li class="alt"><span>unset($sockets[$id]);  </span></li>
<li class=""><span>} else {  </span></li>
<li class="alt">
<span>$result[$id] </span><span class="attribute">.</span><span>= $data;  </span>
</li>
<li class=""><span>}  </span></li>
<li class="alt"><span>}  </span></li>
<li class=""><span>} else {  </span></li>
<li class="alt"><span>/* A time-out means that *all* streams have failed  </span></li>
<li class=""><span>to receive a response. */  </span></li>
<li class="alt"><span>echo "Time-out!n";  </span></li>
<li class=""><span>break;  </span></li>
<li class="alt"><span>}  </span></li>
<li class=""><span>}  </span></li>
<li class="alt"><span>?＞  </span></li>
</ol>

If you run this listing, you will see the output shown below.

http://www.bkjia.com/PHPjc/446460.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/446460.htmlTechArticleThreads are our first consideration when doing projects. How to implement threads in php? Let’s take a look here. Implementation of PHP threads. Many PHP developers believe that due to the missing line in standard PHP...