SimpleSHM 是一个较小的抽象层，用于使用 PHP 操作共享内存，支持以一种面向对象的方式轻松操作内存段。在编写使用共享内存进行存储的小型应用程序时，这个库可帮助创建非常简洁的代码。可以使用 3 个方法进行处理：读、写和删除。从该类中简单地实例化一个对象，可以控制打开的共享内存段。
类对象和测试代码
<?php
//类对象
namespace Simple\SHM;
class Block
{
/**
* Holds the system id for the shared memory block
*
* @var int
* @access protected
*/
protected $id;
/**
* Holds the shared memory block id returned by shmop_open
*
* @var int
* @access protected
*/
protected $shmid;
/**
* Holds the default permission (octal) that will be used in created memory blocks
*
* @var int
* @access protected
*/
protected $perms = 0644;
/**
* Shared memory block instantiation
*
* In the constructor we'll check if the block we're going to manipulate
* already exists or needs to be created. If it exists, let's open it.
*
* @access public
* @param string $id (optional) ID of the shared memory block you want to manipulate
*/
public function __construct($id = null)
{
if($id === null) {
$this->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);
}
}<?php
//测试使用代码
namespace Simple\SHM\Test;
use Simple\SHM\Block;
class BlockTest extends \PHPUnit_Framework_TestCase
{
public function testIsCreatingNewBlock()
{
$memory = new Block;
$this->assertInstanceOf('Simple\\SHM\\Block', $memory);
$memory->write('Sample');
$data = $memory->read();
$this->assertEquals('Sample', $data);
}
public function testIsCreatingNewBlockWithId()
{
$memory = new Block(897);
$this->assertInstanceOf('Simple\\SHM\\Block', $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('Simple\\SHM\\Block', $memory);
$memory->write('Sample 3');
unset($memory);
$memory = new Block;
$data = $memory->read();
$this->assertEquals('Sample 3', $data);
}
}额外说明
<?php
$memory = new SimpleSHM;
$memory->write('Sample');
echo $memory->read();
?>请注意，上面代码里没有为该类传递一个 ID。如果没有传递 ID，它将随机选择一个编号并打开该编号的新内存段。我们可以以参数的形式传递一个编号，供构造函数打开现有的内存段，或者创建一个具有特定 ID 的内存段，如下
<?php
$new = new SimpleSHM(897);
$new->write('Sample');
echo $new->read();
?>神奇的方法 __destructor 负责在该内存段上调用 shmop_close 来取消设置对象，以与该内存段分离。我们将这称为 “SimpleSHM 101”。现在让我们将此方法用于更高级的用途：使用共享内存作为存储。存储数据集需要序列化，因为数组或对象无法存储在内存中。尽管这里使用了 JSON 来序列化，但任何其他方法（比如 XML 或内置的 PHP 序列化功能）也已足够。如下
<?php
require('SimpleSHM.class.php');
$results = array(
'user' => '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);
?>我们成功地将一个数组序列化为一个 JSON 字符串，将它存储在共享内存块中，从中读取数据，去序列化 JSON 字符串，并显示存储的数组。这看起来很简单，但请想象一下这个代码片段带来的可能性。您可以使用它存储 Web 服务请求、数据库查询或者甚至模板引擎缓存的结果。在内存中读取和写入将带来比在磁盘中读取和写入更高的性能。
使用此存储技术不仅对缓存有用，也对应用程序之间的数据交换也有用，只要数据以两端都可读的格式存储。不要低估共享内存在 Web 应用程序中的力量。可采用许多不同的方式来巧妙地实现这种存储，惟一的限制是开发人员的创造力和技能。
