摘要：是一個較小的抽象層，用于使用操作共享內存，支持以一種面向對象的方式輕松操作內存段。在編寫使用共享內存進行存儲的小型應用程序時，這個庫可幫助創建非常簡潔的代碼。不要低估共享內存在應用程序中的力量。

SimpleSHM 是一個較小的抽象層，用于使用 PHP 操作共享內存，支持以一種面向對象的方式輕松操作內存段。在編寫使用共享內存進行存儲的小型應用程序時，這個庫可幫助創建非常簡潔的代碼。可以使用 3 個方法進行處理：讀、寫和刪除。從該類中簡單地實例化一個對象，可以控制打開的共享內存段。

類對象和測試代碼

id = $this->generateID();
        } else {
            $this->id = $id;
        }

        if($this->exists($this->id)) {
            $this->shmid = shmop_open($this->id, "w", 0, 0);
        }
    }

    /**
     * Generates a random ID for a shared memory block
     *
     * @access protected
     * @return int System V IPC key generated from pathname and a project identifier
     */
    protected function generateID()
    {
        $id = ftok(__FILE__, "b");
        return $id;
    }

    /**
     * Checks if a shared memory block with the provided id exists or not
     *
     * In order to check for shared memory existance, we have to open it with
     * reading access. If it doesn"t exist, warnings will be cast, therefore we
     * suppress those with the @ operator.
     *
     * @access public
     * @param string $id ID of the shared memory block you want to check
     * @return boolean True if the block exists, false if it doesn"t
     */
    public function exists($id)
    {
        $status = @shmop_open($id, "a", 0, 0);
        return $status;
    }

    /**
     * Writes on a shared memory block
     *
     * First we check for the block existance, and if it doesn"t, we"ll create it. Now, if the
     * block already exists, we need to delete it and create it again with a new byte allocation that
     * matches the size of the data that we want to write there. We mark for deletion,  close the semaphore
     * and create it again.
     *
     * @access public
     * @param string $data The data that you wan"t to write into the shared memory block
     */
    public function write($data)
    {
        $size = mb_strlen($data, "UTF-8");

        if($this->exists($this->id)) {
            shmop_delete($this->shmid);
            shmop_close($this->shmid);
            $this->shmid = shmop_open($this->id, "c", $this->perms, $size);
            shmop_write($this->shmid, $data, 0);
        } else {
            $this->shmid = shmop_open($this->id, "c", $this->perms, $size);
            shmop_write($this->shmid, $data, 0);
        }
    }

    /**
     * Reads from a shared memory block
     *
     * @access public
     * @return string The data read from the shared memory block
     */
    public function read()
    {
        $size = shmop_size($this->shmid);
        $data = shmop_read($this->shmid, 0, $size);

        return $data;
    }

    /**
     * Mark a shared memory block for deletion
     *
     * @access public
     */
    public function delete()
    {
        shmop_delete($this->shmid);
    }

    /**
     * Gets the current shared memory block id
     *
     * @access public
     */
    public function getId()
    {
        return $this->id;
    }

    /**
     * Gets the current shared memory block permissions
     *
     * @access public
     */
    public function getPermissions()
    {
        return $this->perms;
    }

    /**
     * Sets the default permission (octal) that will be used in created memory blocks
     *
     * @access public
     * @param string $perms Permissions, in octal form
     */
    public function setPermissions($perms)
    {
        $this->perms = $perms;
    }

    /**
     * Closes the shared memory block and stops manipulation
     *
     * @access public
     */
    public function __destruct()
    {
        shmop_close($this->shmid);
    }
}

assertInstanceOf("SimpleSHMBlock", $memory);

        $memory->write("Sample");
        $data = $memory->read();
        $this->assertEquals("Sample", $data);
    }

    public function testIsCreatingNewBlockWithId()
    {
        $memory = new Block(897);
        $this->assertInstanceOf("SimpleSHMBlock", $memory);
        $this->assertEquals(897, $memory->getId());

        $memory->write("Sample 2");
        $data = $memory->read();
        $this->assertEquals("Sample 2", $data);
    }

    public function testIsMarkingBlockForDeletion()
    {
        $memory = new Block(897);
        $memory->delete();
        $data = $memory->read();
        $this->assertEquals("Sample 2", $data);
    }

    public function testIsPersistingNewBlockWithoutId()
    {
        $memory = new Block;
        $this->assertInstanceOf("SimpleSHMBlock", $memory);
        $memory->write("Sample 3");
        unset($memory);

        $memory = new Block;
        $data = $memory->read();
        $this->assertEquals("Sample 3", $data);
    }
}

額外說明

write("Sample");
echo $memory->read();
 
?>

請注意，上面代碼里沒有為該類傳遞一個 ID。如果沒有傳遞 ID，它將隨機選擇一個編號并打開該編號的新內存段。我們可以以參數的形式傳遞一個編號，供構造函數打開現有的內存段，或者創建一個具有特定 ID 的內存段，如下

write("Sample");
echo $new->read();
 
?>

神奇的方法 __destructor 負責在該內存段上調用 shmop_close 來取消設置對象，以與該內存段分離。我們將這稱為 “SimpleSHM 101”。現在讓我們將此方法用于更高級的用途：使用共享內存作為存儲。存儲數據集需要序列化，因為數組或對象無法存儲在內存中。盡管這里使用了 JSON 來序列化，但任何其他方法（比如 XML 或內置的 PHP 序列化功能）也已足夠。如下

 "John",
    "password" => "123456",
    "posts" => array("My name is John", "My name is not John")
);
 
$data = json_encode($results);
 
$memory = new SimpleSHM;
$memory->write($data);
$storedarray = json_decode($memory->read());
 
print_r($storedarray);
 
?>

我們成功地將一個數組序列化為一個 JSON 字符串，將它存儲在共享內存塊中，從中讀取數據，去序列化 JSON 字符串，并顯示存儲的數組。這看起來很簡單，但請想象一下這個代碼片段帶來的可能性。您可以使用它存儲 Web 服務請求、數據庫查詢或者甚至模板引擎緩存的結果。在內存中讀取和寫入將帶來比在磁盤中讀取和寫入更高的性能。

使用此存儲技術不僅對緩存有用，也對應用程序之間的數據交換也有用，只要數據以兩端都可讀的格式存儲。不要低估共享內存在 Web 應用程序中的力量。可采用許多不同的方式來巧妙地實現這種存儲，惟一的限制是開發人員的創造力和技能。