How to implement multi-process programming in PHP

This article mainly introduces the PHP multi-process programming method, and analyzes the concepts, usage, related functions and usage skills of PHP multi-process programming in more detail. Friends in need can refer to it

The first step:

$ php -m command checks whether php has pcntl and posix extensions installed. If not, install them

Usage scenarios:

1. A large number of time-consuming network operations are required.
2. A large number of calculations are required, and the system has multiple CPUs. In order to provide users with a faster experience, a task is divided into several A small task, finally merged.

Commonly used functions for multiple processes:

pcntl_alarm — Set an alarm clock signal for the process
pcntl_errno — Alias pcntl_strerror
pcntl_exec —Execute the specified program in the current process space
pcntl_fork—Create a child process and generate a branch (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 return value of fork is the child process number, while the child process gets 0.
pcntl_get_last_error — Retrieve the error number set by the last pcntl function which failed
pcntl_getpriority — Get the priority of any process
pcntl_setpriority — Modify the priority of any process
pcntl_signal_dispatch — Call a handler waiting for a signal
pcntl_signal — Install a signal handler
pcntl_sigprocmask — Set or retrieve blocking signals
pcntl_sigtimedwait — Signal waiting with timeout mechanism
pcntl_sigwaitinfo — Wait for signals
pcntl_strerror — Retrieve the system error message associated with the given errno
pcntl_wait — Wait for or return the child process status of fork
pcntl_waitpid — Wait for or return the child process status of fork
pcntl_wexitstatus — Returns the return code of an interrupted child process
pcntl_wifexited — Checks whether the status code represents a normal exit.
pcntl_wifsignaled — Check whether the child process status code represents an interruption due to a signal
pcntl_wifstopped — Check whether the child process is currently stopped
pcntl_wstopsig — Return the signal that causes the child process to stop
pcntl_wtermsig — Return the signal that causes the child process to interrupt

Example 1:

<?php
//最早的进程，也是父进程
$parentPid = getmypid();
echo &#39;原始父进程：&#39; . $parentPid . PHP_EOL;
//创建子进程,返回子进程id
$pid = pcntl_fork();
if( $pid == -1 ){
  exit("fork error");
}
//pcntl_fork 后，父进程返回子进程id，子进程返回0
echo &#39;ID : &#39; . $pid . PHP_EOL;
if( $pid == 0 ){
  //子进程执行pcntl_fork的时候，pid总是0，并且不会再fork出新的进程
  $mypid = getmypid(); // 用getmypid()函数获取当前进程的PID
  echo &#39;I am child process. My PID is &#39; . $mypid . &#39; and my fathers PID is &#39; . $parentPid . PHP_EOL;
} else {
  //父进程fork之后，返回的就是子进程的pid号，pid不为0
  echo &#39;Oh my god! I am a father now! My childs PID is &#39; . $pid . &#39; and mine is &#39; . $parentPid . PHP_EOL;
}
$aa = shell_exec("ps -af | grep index.php");
echo $aa;

Example 2: Open multiple child processes to avoid fork flooding

<?php
//最早的进程，也是父进程
$parentPid = getmypid();
echo &#39;原始父进程：&#39; . $parentPid . PHP_EOL;
//开启十个子进程
for($i = 0; $i < 10; $i++) {
  $pid = pcntl_fork();
  if($pid == -1) {
    echo "Could not fork!\n";
    exit(1);
  }
  //子进程
  if(!$pid) {
    //child process workspace
    echo &#39;子进程：&#39; . getmypid() . PHP_EOL;
    exit(); //子进程逻辑执行完后，马上退出，以免往下走再fork子进程，不好控制  
  } else {
    echo &#39;父进程：&#39; . getmypid() . PHP_EOL;
  }
}
echo getmypid() . PHP_EOL;
$aa = shell_exec("ps -af | grep index.php");
echo $aa;

Note:

Use the multi-process function through the pcntl_XXX series of functions. Note: pcntl_XXX can only run in the php CLI (command line) environment. In the web server environment, unpredictable results will occur, please use with caution!

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