php操作共享内存shmop类及简单使用测试（代码）

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。

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