PHP uses pcntl_fork to implement multi-process downloading of images, _PHP tutorial

PHP uses pcntl_fork to implement multi-process downloading of images,

The example in this article describes how PHP uses pcntl_fork to implement multi-process downloading of images. Share it with everyone for your reference. The specific analysis is as follows:

PHP pcntl_fork — Generates a branch, a child process, at the current position of the current process. Annotation: fork creates a child process. Both the parent process and the child process continue to execute from the fork position. The difference is that during the execution of the parent process , the fork return value obtained is the child process number, and the child process gets 0.

Note: PHP has a pcntl_fork function that can implement multi-process, but it needs to load the pcntl extension, and this extension can only be compiled under Linux.

1. First compile pcntl.so under ubuntu. I couldn’t find the pcntl package under my ubuntu, so I created a folder and downloaded the entire PHP package. I found the pcntl package in it and ran the following command. The code is as follows:

Copy code The code is as follows:

# mkdir php
# cd php
# apt-get source php5
# cd php5-(WHATEVER_RELEASE)/ext/pcntl
# phpize
# ./configure (Note 1)
# make
# The make install phpize command is used to prepare the compilation environment for PHP plug-in modules

A successful installation will create extname.so and place it in the plug-in module directory of PHP (default stored in /usr/lib/php/modules/). You need to adjust php.ini and add extension=extname.so. This plug-in module can only be used after one line.

Example:

Copy code The code is as follows:

void pcntl_exec(string $path [,array $args [,array $envs ]])

pcntl_exec — Execute the specified program in the current process space, the code is as follows:

Copy code The code is as follows:

$cmds=array(
array('/home/jerry/projects/www/test2.php'),
array('/home/jerry/projects/www/test3.php')
);

foreach($cmds as $cmd){
          $pid=pcntl_fork();
If($pid==-1){
//Process creation failed
                                            echo 'Return -1 when creating a child process fails';
exit(-1);
          }
          else if($pid){
//The parent process will get the child process number, so here is the logic executed by the parent process
pcntl_wait($status,WNOHANG);
          }
         else{
//Subprocess processing logic
               sleep(5);
​​​​​​ pcntl_exec('/usr/bin/php',$cmd);
exit(0);
          }
}

For example, to download multiple images simultaneously, the code is as follows:

Copy code The code is as follows:

#!/usr/bin/php
//Web page address to be crawled
$url = 'http://www.bkjia.com';
$content = file_get_contents($url);
preg_match_all('/ echo "Found".count($matches)."Pictures n";

list($sm, $ss) = explode(" ", microtime());
foreach ($matches as $k => $val)
{
$pid[$k] = pcntl_fork();
if(!$pid[$k])
{
download($url, $val);
// The child process must exit, otherwise it will perform recursive multi-processing. The parent process must not exit, otherwise it will terminate the multi-process
exit(0);
}

if ($pid[$k])
{
// pcntl_waitpid($pid[$k], $status, WUNTRACED);
}

}
echo "Download completedn";

list($em, $es) = explode(" ", microtime());

echo "Time taken:",($es+$em) - ($ss + $sm),"n";
/**
* Grab web images
*
​*/
function download($url, $val)
{
$pic_url = $val[1];
if (strpos($val[1], '//') !== false)
{
;
}
elseif (preg_match('@^(.*?)/@', $val[1], $inner_matches) == 0)
{
$pic_url = $url.$val[1];
}
elseif (preg_match('@[:.]@', $inner_matches[1], $tmp_matches) == 0)
{
$pic_url = $url.$val[1];
}

$pic = file_get_contents($pic_url);

if ($pic === false)
{
Return;
}

preg_match('@/([^/]+)$@', $pic_url, $tmp_matches);
// You can use assert to handle exceptions
$pic_file_name = $tmp_matches[1];
$f = fopen("tmp/".$pic_file_name, "wb"); #
fwrite($f, $pic);
fclose($f);
}

/* End of file pcntl_fork.php */
?>

I hope this article will be helpful to everyone’s PHP programming design.

http://www.bkjia.com/PHPjc/928221.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/928221.htmlTechArticlePHP uses pcntl_fork to implement multi-process downloading of images. This article describes the example of PHP using pcntl_fork to implement multi-process downloading of images. method. Share it with everyone for your reference. Detailed analysis...