php Pthread 多线程 (四) 共享内存

有些时候我们希望在多个线程中共享一些需要的数据，我们可以使用shmop扩展。

<?php

class Count extends Thread {

    private $name = '';

    public function __construct($name) {

        $this->name = $name;

    }

    public function run() {

        //在Linux下可以使用sysvshm的扩展, shm_等函数

        //共享内存段的key

        $shmKey = 123;

        //创建共享内存段

        $shmId = shmop_open($shmKey, 'c', 0777, 64);

        //读取共享内存数据

        $data = trim(shmop_read($shmId, 0, 64));

        $data = intval($data);

        ++$data;

        shmop_write($shmId, $data, 0);

        echo "thread {$this->name} data {$data} \r\n";

        //删除关闭共享内存段

        shmop_delete($shmId);

        shmop_close($shmId);

    }

}

$threads = array();

for($ix = 0; $ix < 10; ++$ix) {

    $thread = new Count($ix);

    $thread->start();

    $threads[] = $thread;

}

foreach($threads as $thread) {

    $thread->join();

}

如上代码可以正常运行。结果如下：

但是如果我把代码改成如下情况：

<?php

class Count extends Thread {

    private $name = '';

    private $shmId = '';

    public function __construct($name, $shmId) {

        $this->name = $name;

        $this->shmId = $shmId;

    }

    public function run() {

        $data = shmop_read($this->shmId, 0, 64);

        $data = intval($data);

        ++$data;

        shmop_write($this->shmId, $data, 0);

        echo "thread {$this->name} data {$data} \r\n";

    }

}

//在Linux下可以使用sysvshm的扩展

//共享内存段的key

$shmKey = 123;

//创建共享内存段

$shmId = shmop_open($shmKey, 'c', 0777, 64);

//写入数据到共享内存段

shmop_write($shmId, '1', 0);

$threads = array();

for($ix = 0; $ix < 10; ++$ix) {

    $thread = new Count($ix, $shmId);

    $thread->start();

    $threads[] = $thread;

}

foreach($threads as $thread) {

    $thread->join();

}

echo shmop_read($shmId, 0, 64);

//删除关闭共享内存段

shmop_delete($shmId);

shmop_close($shmId);

上述代码就会出现如下警告：

Warning: shmop_read(): no shared memory segment with an id of [4] in D:\wwwroot\

thread\demo6.php on line 13

PHP Warning: shmop_write(): no shared memory segment with an id of [4] in D:\ww

wroot\thread\demo6.php on line 16

字面意思是无共享内存段，在new线程的过程中我们已经通过构造函数把$shmId传进去了，为什么会出现无共享内存段？

我们知道shmop_open函数成功创建共享内存段后会返回一个ID，该类型是int型。当我们把该ID传入到子线程中时，子线程是无法通过该ID找到共享内存段。

巴特西

php Pthread 多线程 (四) 共享内存

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