php信号量和共享内存分别是什么

echo "parent progress pid:{$parentPid}\n";

$childList = array();

// 创建共享内存,创建信号量,定义共享key

$shm_id = ftok(__FILE__,'m');

$sem_id = ftok(__FILE__,'s');

$shareMemory = shm_attach($shm_id);

$signal = sem_get($sem_id);

const SHARE_KEY = 1;

// 生产者

function producer(){

    global $shareMemory;

    global $signal;

    $pid = posix_getpid();

    $repeatNum = 5;

    for ( $i = 1; $i <= $repeatNum; $i++) {

        // 获得信号量

        sem_acquire($signal);

        if (shm_has_var($shareMemory,SHARE_KEY)){

            // 有值,加一

            $count = shm_get_var($shareMemory,SHARE_KEY);

            $count ++;

            shm_put_var($shareMemory,SHARE_KEY,$count);

            echo "({$pid}) count: {$count}\n";

        }else{

            // 无值,初始化

            shm_put_var($shareMemory,SHARE_KEY,0);

            echo "({$pid}) count: 0\n";

        }

        // 用完释放

        sem_release($signal);

        $rand = rand(1,3);

        sleep($rand);

    }

}

function createProgress($callback){

    $pid = pcntl_fork();

    if ( $pid == -1) {

        // 创建失败

        exit("fork progress error!\n");

    } else if ($pid == 0) {

        // 子进程执行程序

        $pid = posix_getpid();

        $callback();

        exit("({$pid})child progress end!\n");

    }else{

        // 父进程执行程序

        return $pid;

    }

}

// 3个写进程

for ($i = 0; $i < 3; $i ++ ) {

    $pid = createProgress('producer');

    $childList[$pid] = 1;

    echo "create producer child progress: {$pid} \n";

}

// 等待所有子进程结束

while(!empty($childList)){

    $childPid = pcntl_wait($status);

    if ($childPid > 0){

        unset($childList[$childPid]);

    }

}

// 释放共享内存与信号量

shm_remove($shareMemory);

sem_remove($signal);

echo "({$parentPid})main progress end!\n";