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 and 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 the parent process During the execution 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 the pcntl extension needs to be loaded, and it can only be compiled under Linux. This extension.

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 :

# mkdir php 
# cd php 
# apt-get source php5 
# cd php5-(WHATEVER_RELEASE)/ext/pcntl 
# phpize 
# ./configure (注一) 
# make 
# make install phpize 命令是用来准备 PHP 外挂模块的编译环境的

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 Only after this line can the plug-in module be used.

Example:

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:

$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){ 
        //进程创建失败 
            echo '创建子进程失败时返回-1'; 
            exit(-1); 
        } 
        else if($pid){ 
        //父进程会得到子进程号，所以这里是父进程执行的逻辑 
            pcntl_wait($status,WNOHANG); 
        } 
        else{ 
        //子进程处理逻辑 
            sleep(5); 
            pcntl_exec('/usr/bin/php',$cmd); 
            exit(0); 
        } 
}

Example, the example is to download multiple pictures simultaneously, the code is as follows:

#!/usr/bin/php 
<?php 
// 需要抓取的网页地址 
$url = 'http://www.php.cn'; 
$content = file_get_contents($url); 
preg_match_all('/<imgs+src="(.*?)"/', $content, $matches,PREG_SET_ORDER); 
echo "已发现".count($matches)."张图片n"; 
 
list($sm, $ss) = explode(" ", microtime()); 
foreach ($matches as $k => $val) 
{ 
 $pid[$k] = pcntl_fork(); 
 if(!$pid[$k]) 
 { 
  download($url, $val); 
  // 子进程要exit否则会进行递归多进程，父进程不要exit否则终止多进程 
  exit(0); 
 } 
 
 if ($pid[$k]) 
 { 
//    pcntl_waitpid($pid[$k], $status, WUNTRACED); 
 } 
 
} 
echo "下载完成n"; 
 
list($em, $es) = explode(" ", microtime()); 
 
echo "用时：",($es+$em) - ($ss + $sm),"n"; 
/** 
 * 抓取网页图片 
 *  
 */ 
function download($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); 
 // 可使用assert处理异常 
 $pic_file_name = $tmp_matches[1]; 
 $f = fopen("tmp/".$pic_file_name, "wb"); # 
 fwrite($f, $pic); 
 fclose($f); 
} 
 
/* End of file pcntl_fork.php */ 
?>

Hope this article explains It will be helpful for everyone's PHP programming.

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