About PHP multi-process programming (detailed code explanation)

php multi-process programming

PHP’s process control support implements Unix-style process creation and program execution, Signal handling and process interruption. Process control cannot be used in a Web server environment and may cause unexpected results when used in a Web serving environment.

pcntl function

pcntl_fork(): Generates a branch (child process) at the current position of the current process.

Translation Note: 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 is the child process number. What the child process gets is 0

<?php
$pid = pcntl_fork();
//父进程和子进程都会执行下面代码
if ($pid == -1) {
    //错误处理：创建子进程失败时返回-1.
     die(&#39;could not fork&#39;);
} 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); //等待子进程中断，防止子进程成为僵尸进程。
} else {
     //子进程得到的$pid为0, 所以这里是子进程执行的逻辑。
    exit();//子进程执行完后应该退出，不然会继续执行后面的逻辑
}

● pcntl_wait(int &$status[, int $options = 0]): wait for or return the child process status of fork, equivalent to pcntl_waitpid(-1,int &$ status[,int $options = 0])

● pcntl_waitpid(int $pid, int &$status[,int $options = 0]) $status is used as a parameter of the following function

● pcntl_wifexited(int $status) checks whether the child process status code represents a normal exit,

● pcntl_wexistatus(int $status) returns an interrupted child process return code, which is only valid for normal interruption

● pcntl_wifsignaled(int $status) Check whether the child process exited by an uncaught signal. Returns true if yes, false if not

● pcntl_wtermsig(int $status) returns the signal that caused the child process to be interrupted. It is valid when pcntl_wifsignaled returns true

<?php
 echo "主进程\n";
 $pid = pcntl_fork();
 //父进程和子进程都会执行这些代码
 if($pid == -1 ){
     //创建子进程失败会返回-1
     throw new Exception (&#39;fork error on Task object&#39;);
 }else if($pid){
     //创建成功会父进程会得到子进程的pid
     echo "等待子进程执行";
     pcntl_wait($status);//等待子进程中断
     echo "子进程执行状态：";
     echo "是否正常退出：",pcntl_wifexited($status),"\n";
     echo "子进程返回的代码：",pcntl_wexitstatus($status),"\n";//仅在pcntl_wifexited返回true时生效,只能是int，输出123
     echo "子进程是否是由于某个未捕获的信号退出的：",pcntl_wifsignaled($status),"\n";//如果是kill -9|-15 杀死的进程返回true
     echo "导致子进程中断的信号：",pcntl_wtermsig($status),"\n"; 输出 9 | 15
     var_dump($status);
 }else{
     //创建成功子进程会得到pid=0
     sleep(2);
     echo "子进程执行完毕\n";
         exit(123)
 }

● pcntl_alarm(int $seconds): is The process sets an alarn alarm signal

● pcntl_signal(int $signo, callback $handler [, bool $restart_syscalls = true ]) installs a new signal handler for the specified signal

● pcntl_signal_get_handler (int $signo) Get the processing function of the specified signal

<?php
 
echo "设置3秒之后发送闹钟信号\n";
pcntl_alarm(3);
 
function dealSigalarm(){
    echo "收到信号 SIGALRM \n退出程序。。。\n";
    exit();
}
 
echo "安装信号处理器\n";
pcntl_signal(SIGALRM,"dealSigalarm");//对于不能被阻塞、处理和忽略的信号，php为这些时间注册信号处理函数会产生一个致命错误SIGSTOP,SIGKILL
var_dump(pcntl_signal_get_handler(SIGUSR1));//输出dealSigalarm
pcntl_signal(SIGUSR1,function(){
    echo "收到用户自定义信号\n";
});
$i = 1;
while(1){
    sleep(1);
    echo $i++,"\n";
    echo "分发... \n";
    pcntl_signal_dispatch();
};

● pcntl_getpriority( int $pid = getmypid() [, int $process_identifier = PRIO_PROCESS ]) Get the priority of the process

● pcntl_setpriority (int $priority [, int $pid = getmypid() [, int $process_identifier = PRIO_PROCESS]]) Set the priority of the process

● getmypid() Get the pid of the current php process

● posix_getpid() gets the pid of the current process

<?php
 /**
 * php进程的优先级
 */
 
 for($i = 1;$i<=5;$i++){
     $pid = pcntl_fork();
     if($pid == -1){
         throw new Exception("fork error on task object");
     }else if ($pid){
         pcntl_wait($status);
     }else{
         $end_time = time()+3;
         $k = 0;
         while(time()<=$end_time){
             $k++;
         }
         $pid = getmypid();
         echo "当前进程id:".$pid,"优先级:",pcntl_getpriority($pid);
         pcntl_setpriority($i);
         echo "修改之后的优先级为：",pcntl_getpriority(),"\n";
         echo "执行了进程{$i} {$k}次\r\n";
         exit();
     }
 }

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