关于php多进程编程（代码详解）

<?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('could not fork');
} 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
}

<?php
 echo "主进程
";
 $pid = pcntl_fork();
 //父进程和子进程都会执行这些代码
 if($pid == -1 ){
 //创建子进程失败会返回-1
 throw new Exception ('fork error on Task object');
 }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($status),"
";
 echo "子进程返回的代码：",pcntl_wexitstatus($status),"
";//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($status),"
";//如果是kill -9|-15 杀死的进程返回true
 echo "导致子进程中断的信号：",pcntl_wtermsig($status),"
"; 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
";
 exit(123)
 }

<?php
 
echo "设置3秒之后发送闹钟信号
";
pcntl_alarm(3);
 
function dealSigalarm(){
 echo "收到信号 SIGALRM 
退出程序。。
";
 exit();
}
 
echo "安装信号处理器
";
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
";
});
$i = 1;
while(1){
 sleep(1);
 echo $i++,"
";
 echo "分发... 
";
 pcntl_signal_dispatch();
};

<?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(),"
";
 echo "执行了进程{$i} {$k}次
";
 exit();
 }
 }