PHP uses Pcntl_fork to implement a multi-process download picture method, _php tutorial

PHP uses Pcntl_fork to implement a multi-process download picture method,

This article explains how PHP uses Pcntl_fork to implement multi-process download images. Share to everyone for your reference. The specific analysis is as follows:

PHP pcntl_fork-in the current position of the present process to create a branch, sub-process, the fork is the creation of a child process, the parent process and the child process from the position of the fork to continue to execute, different from the parent process, the resulting fork return value is the child process number, and the sub-process gets 0.

Note: PHP has a pcntl_fork function to implement multi-process, but to load pcntl extension, and only under Linux to compile this extension.

1. First compile pcntl.so under Ubuntu, my Ubuntu can't find Pcntl package, so create a folder to download the entire PHP package, found inside the PCNTL package run the following command, the code is as follows:
Copy the Code code as follows: # mkdir PHP
# CD PHP
# Apt-get Source PhP5
# CD php5-(whatever_release)/ext/pcntl
# phpize
#./configure (Note i)
# make
# make install Phpize command is used to prepare the PHP plugin for the build environment

A successful installation will be built extname.so and placed in the PHP plug-in module directory (preset stored in the/usr/lib/php/modules/), need to adjust php.ini, add extension=extname.so You can use this plug-in after this line.

Example: copy code code as follows: void Pcntl_exec (String $path [, array $args [, array $envs]]

pcntl_exec-executes the specified program in the current process space, with the following code:
Copy CodeThe 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 ' failed to create child process returns-1 ';
Exit (-1);
}
else if ($pid) {
The parent process gets the child process number, so this is the logic that the parent process executes
Pcntl_wait ($status, Wnohang);
}
else{
Subprocess Process Logic
Sleep (5);
Pcntl_exec ('/usr/bin/php ', $cmd);
Exit (0);
}
}
example, the example of multi-image synchronization download, the code is as follows:
Copy CodeThe code is as follows: #!/usr/bin/php
<?php
Web address to crawl
$url = ' http://www.bkjia.com ';
$content = file_get_contents ($url);
Preg_match_all ('/echo ' found. Count ($matches). " Picture n ";

List ($SM, $ss) = Explode ("", Microtime ());
foreach ($matches as $k = $val)
{
$pid [$k] = Pcntl_fork ();
if (! $pid [$k])
{
Download ($url, $val);
Child process to exit otherwise a recursive multi-process is performed, and the parent process does not exit or terminate the multi-process
Exit (0);
}

if ($pid [$k])
{
Pcntl_waitpid ($pid [$k], $status, wuntraced);
}

}
echo "Download complete n";

List ($em, $es) = Explode ("", Microtime ());

echo "Spents:", ($es + $em)-($ss + $sm), "n";
/**
* Crawl Web Images
*
*/
function Download ($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);
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 is helpful to everyone's PHP programming.

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