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以下来介绍eAccelerator及eAccelerator详细配置
目录：
一、eAccelerator介绍
1、背景
2、原理
二、安装和配置
1、支持平台
2、系统要求
3、安装
4、php.ini文件配置
5、验证安装
三、使用eAccelerator开发PHP代码
1、API文档和接口说明
2、开发范例
四、附录和参考资料
一、eAccelerator介绍
1、背景
eAccelerator 是一个免费开源的PHP加速、优化、编译和动态缓存的项目，它可以通过缓存PHP代码编译后的结果来提高PHP脚本的性能，使得一向很复杂和离我们很远的PHP脚本编译问题完全得到解决。通过使用eAccelerator，可以优化你的PHP代码执行速度，降低服务器负载，可以提高PHP应用执行速度最高达10倍。
eAccelerator 项目诞生于2004年，当时它是作为 Turck MMCache 项目的一个分支提出并投入开发的。 Turck MMCache 由 Dmitry Stogov 开发，是个非常优秀的PHP内存缓存加速系统，如今仍然有很大部分 eAccelerator 的代码应用到该项目中，目前该项目有很长时间没有更新了，对于最新的PHP5.x的支持还未推出。
2、原理
eAccelerator 通过把经过编译后的PHP代码缓存到共享内存中，并在用户访问的时候直接调用从而起到高效的加速作用。它的效率非常高，从创建共享内存到查找编译后的代码都在非常短的时间内完成，对于不能缓存到共享内存中的文件和代码，eAccelerator还可以把他们缓存到系统磁盘上。
eAccelerator 同样还支持PHP代码的编译和解释执行，你可以通过encoder.php脚本来对php代码进行编译达到保护代码的目的，经过编译后的代码必须运行在安装了eAccelerator的环境下。eAccelerator编译后的代码不能被反编译，它不象其他一些编译工具那样可以进行反编译，这将使得代码更加安全和高效。
二、eAccelerator安装配置
1、支持平台
由于aAccelerator提供了大部分基于共享内存的API，所以在*nix的平台上将得到更好的支持，虽然也发布了基于windows平台的binary版本，但我在这里就只提供基于*nix平台的配置和说明，目前可以支持的平台包括Linux, FreeBSD, OpenBSD, Mac OS X, Solaris, AIX en HP-UX。
2、系统要求
php4 or php5
autoconf
automake
libtool
m4
eAccelerator 只支持使用 mod_php 或者 fastcgi mode 安装的PHP
3、安装
先去eAccelerator官方下载最新版的源码包：eaccelerator-0.9.5-beta.tar.bz2
#tar -zxvf ./eaccelerator-0.9.5-beta2.tar.bz2
#cd eaccelerator-0.9.5-beta2
#export PHP_PREFIX="/usr/local" （把PHP安装目录导入到环境变量，FreeBSD默认是/usr/local）
#$PHP_PREFIX/bin/phpize
#./configure --enable-eaccelerator=shared --with-php-config=$PHP_PREFIX/bin/php-config
#make
#make install
4、ini文件配置
安装完成，下面开始配置php.ini文件,eAccelerator提供了两种配置和调用方式，分别如下。
安装为 Zend extension 模式：
zend_extension="/usr/local/lib/php/20050922/eaccelerator.so"
eaccelerator.shm_size="16"
eaccelerator.cache_dir="/tmp/eaccelerator"
eaccelerator.enable="1"
eaccelerator.optimizer="1"
eaccelerator.check_mtime="1"
eaccelerator.debug="0"
eaccelerator.log_file = "/var/log/httpd/eaccelerator_log"
eaccelerator.filter=""
eaccelerator.shm_max="0"
eaccelerator.shm_ttl="0"
eaccelerator.shm_prune_period="0"
eaccelerator.shm_only="0"
press="1"
press_level="9"
如果你使用了thread safe模式安装的PHP，你必须使用 “zend_extension_ts” 替换第一行的 “zend_extension”.
安装为 PHP extension 模式：（这是大部分采用的方式）
extension="eaccelerator.so"
eaccelerator.shm_size="16"
eaccelerator.cache_dir="/tmp/eaccelerator"
eaccelerator.enable="1"
eaccelerator.optimizer="1"
eaccelerator.check_mtime="1"
eaccelerator.debug="0"
eaccelerator.log_file = "/var/log/httpd/eaccelerator_log"
eaccelerator.filter=""
eaccelerator.shm_max="0"
eaccelerator.shm_ttl="0"
eaccelerator.shm_prune_period="0"
eaccelerator.shm_only="0"
press="1"
press_level="9"
有关php.ini文件的详细配置说明，请参照源码目录的README文档或者访问官方文档：ini setting
完成安装配置后，我们最后要创建缓存目录
#mkdir /tmp/eaccelerator
#chmod 777 /tmp/eaccelerator
5、验证安装结果
通过浏览器访问您的phpinfo()页面或者运行 php -i 得到php配置信息，里面如果看到类似下面的信息就表示安装成功了。
This program makes use of the Zend Scripting Language Engine:
Zend Engine v2.1.0, Copyright (c) 1998-2006 Zend Technologies
with eAccelerator v0.9.5-beta2, Copyright (c) 2004-2006 eAccelerator, by eAccelerator
我的机器上同时还安装了Zend Optimizer3.0.1，所以看到的信息如下：
This program makes use of the Zend Scripting Language Engine:
Zend Engine v2.1.0, Copyright (c) 1998-2006 Zend Technologies
with eAccelerator v0.9.5-beta2, Copyright (c) 2004-2006 eAccelerator, by eAccelerator
with Zend Extension Manager v1.0.10, Copyright (c) 2003-2006, by Zend Technologies
with Zend Optimizer v3.0.1, Copyright (c) 1998-2006, by Zend Technologies
如果你打开了eAccelerator的debug选项，可以从日志中看到类似下面的信息
#tail /var/log/httpd/eAccelerator_log
EACCELERATOR hit: "/var/
EACCELERATOR hit: "/var/
EACCELERATOR hit: "/var/
EACCELERATOR hit: "/var/
EACCELERATOR hit: "/var/
以上信息表示文件都得到了缓存和命中。
至此，我们就完成了全部的安装和配置，好好享受eAccelerator带给你的惊喜吧，根据Michael的测试，效果的确相当的好。
三、在PHP中可以使用eAccelerator的API开发
1、API和文档说明：
eAccelerator提供了便捷便捷而又稳定的本机缓存实现方式，由于大部分代码实现基于共享内存，所以只能在*nix平台中使用，Windows平台Michael就暂时不知道何时有这方面的支持了。
eAccelerator提供如下的API接口和文件：（下述文件均在源码包的doc/php/目录下）
文件列表：
cache.php
dasm.php
encoder.php
info.php
loader.php
session.php
shared_memory.php
接口列表：
array eaccelerator_cached_scripts ()
void eaccelerator_cache_output (string $key, string $eval_code, [int $ttl = 0])
void eaccelerator_cache_page (string $key, [int $ttl = 0])
void eaccelerator_cache_result (string $key, string $code, [int $ttl = 0])
void eaccelerator_caching (boolean $flag)
void eaccelerator_clean ()
void eaccelerator_clear ()
array eaccelerator_dasm_file (mixed $filename)
mixed eaccelerator_encode (mixed $src, [mixed $prefix = ''], [string $pre_content = ''], [string $post_content = ''])
void eaccelerator_gc ()
mixed eaccelerator_get (string $key)
array eaccelerator_info ()
array eaccelerator_list_keys ()
void eaccelerator_load ()
boolean eaccelerator_lock (string $key)
void eaccelerator_optimizer (boolean $flag)
void eaccelerator_purge ()
boolean eaccelerator_put (string $key, mixed $value, [int $ttl = 0])
array eaccelerator_removed_scripts ()
boolean eaccelerator_rm (string $key)
void eaccelerator_rm_page (string $key)
boolean eaccelerator_set_session_handlers ()
boolean eaccelerator_unlock (string $key)
有关上述文档详细说明请参考官方文档：API Documents
下面有部分网友翻译后的接口说明：
eaccelerator_put($key, $value, $ttl=0)
将 $value 以 $key 为键名存进缓存(php4下支持对像类型，看源码好像zend2里不支持了)，$ttl 是这个缓存的生命周期，单位是秒，省略该参数或指定为 0 表示不限时，直到服务器重启清空为止。
eaccelerator_get($key)
根据 $key 从缓存中返回相应的 eaccelerator_put() 存进去的数据，如果这项缓存已经过期或不存在那么返回值是 NULL
eaccelerator_rm($key)
根据 $key 移除缓存
eaccelerator_gc()
移除清理所有已过期的 key
eaccelerator_lock($key)
为 $key 加上锁定操作，以保证多进程多线程操作时数据的同步。需要调用 eaccelerator_unlock($key) 来释放这个锁或等待程序请求结束时自动释放这个锁。
例如:
<?php
eaccelerator_lock("count");
eaccelerator_put("count",eaccelerator_get("count")+1));
?>
eaccelerator_unlock($key)
根据 $key 释放锁
eaccelerator_cache_output($key, $eval_code, $ttl=0)
将 $eval_code 代码的输出缓存 $ttl 秒，（$ttl参数同 eacclerator_put）
例如：
eaccelerator_cache_result($key, $eval_code, $ttl=0)
将 $eval_code 代码的执行结果缓存 $ttl 秒，（$ttl参数同 eacclerator_put），类似 cache_output
例如：
eaccelerator_cache_page($key, $ttl=0)
将当前整页缓存 $ttl 秒。
例如：
<?php
eaccelerator_cache_page($_SERVER['PHP_SELF'].'?GET='.serialize($_GET),30);
echo time();
phpinfo();
?>
eaccelerator_rm_page($key)
删除由 eaccelerator_cache_page() 执行的缓存，参数也是 $key
2、PHP代码中使用eAccelerator加速
下面有一个测试的代码，你可以测试一下eAccelerator强大的威力：（该代码在 cli 模式下可能无效）
class test_cache {
var $pro = 'hello';
function test_cache() {
echo "Object Created!
\n";
}
function func() {
echo ', the world!';
}
function now($t) {
echo date('Y-m-d H:i:s', $t);
}
}
$tt = eaccelerator_get("test_tt");
if (!$tt)
{
$tt = new test_cache;
eaccelerator_put("test_tt", $tt);
echo "no cached!
\n";
}
else {
echo "cached
\n";
}
echo $tt->pro;
$tt->func();
$tt->now(time() + 86400);
?>
另外，据说在著名的vBulletin版里面已经集成了对eAccelerator的支持，下面是一段来自vBulletin里面的代码
// #############################################################################
// eAccelerator
/**
* Class for fetching and initializing the vBulletin datastore from eAccelerator
*
* @package vBulletin
* @version $Revision: 0.1 $
* @date $Date: 2005/06/12 13:14:18 $
*/
class vB_Datastore_eAccelerator extends vB_Datastore
{
/**
* Fetches the contents of the datastore from eAccelerator
*
* @param array Array of items to fetch from the datastore
*
* @return void
*/
function fetch($itemarray)
{
if (!function_exists('eaccelerator_get'))
{
trigger_error("eAccelerator not installed", E_USER_ERROR);
}
foreach ($this->defaultitems AS $item)
{
$this->do_fetch($item);
}
if (is_array($itemarray))
{
foreach ($itemarray AS $item)
{
$this->do_fetch($item);
}
}
$this->check_options();
// set the version number variable
$this->registry->versionnumber =& $this->registry->options['templateversion'];
}
/**
* Fetches the data from shared memory and detects errors
*
* @param string title of the datastore item
*
* @return void
*/
function do_fetch($title)
{
$data = eaccelerator_get($title);
if ($data === null)
{ // appears its not there, lets grab the data, lock the shared memory and put it in
$data = '';
$dataitem = $this->dbobject->query_first("
SELECT title, data FROM " . TABLE_PREFIX . "datastore
WHERE title = '" . $this->dbobject->escape_string($title) ."'
");
if (!empty($dataitem['title']))
{
$data =& $dataitem['data'];
$this->build($dataitem['title'], $dataitem['data']);
}
}
$this->register($title, $data);
}
/**
* Updates the appropriate cache file
*
* @param string title of the datastore item
*
* @return void
*/
function build($title, $data)
{
if (!function_exists('eaccelerator_put'))
{
trigger_error("eAccelerator not installed", E_USER_ERROR);
}
eaccelerator_lock($title);
eaccelerator_put($title, $data);
eaccelerator_unlock($title);
}
}
配置说明：
eaccelerator.shm_size
This setting will allow you to control the amount of shared memory eAccelerator should allocate to cache PHP scripts. The number sets the amount of memory in megabytes. Setting this value to 0 will use the default size.
eaccelerator.shm_size = "0"
On Linux the maximum amount of memory a process can allocate is limited by the number set in /proc/sys/kernel/shmmax. Allocating more than this value will result in eAccelerator failing to initialise. The size in this file is given in bytes. You can raise this amount with:
echo value > /proc/sys/kernel/shmmax
Where value is the size in bytes you want to use. This value is reset to the default value evertime you reboot, but you can raise it permanently by adding the amount you need in /etc/sysctl.conf. This is done by adding:
kernel.shmmax = value
eaccelerator.cache_dir
This directory is used for the disk cache. eAccelerator stores precompiled code, session data, content and user entries here. The same data can be stored in shared memory (for quicker access). The default value is "/tmp/eaccelerator".
eaccelerator.cache_dir = "/tmp/eaccelerator"
This is easy because that directory is easily writable to everyone, and mounted with noexec. However, it isn't the best because on a lot of systems this directory is cleared on reboot. A better place is /var/cache/eaccelerator. Create the directory and make sure it's writable to the process eAccelerator runs under.
A safe bet is making it world writeable, a safer and cleaner way is making the user php runs under (most of the time the same user as apache or lighttpd) the owner and set 0644 permissions.
The lazy way:
mkdir /tmp/eaccelerator
chmod 0777 /tmp/eaccelerator
eaccelerator.enable
With this setting you can enable or disable eAccelerator. This may seem like a pretty stupid setting, but it can be very useful. For example this setting can also be used in the vhost section of the Apache configuration. It allows you to disable eAccelerator for a certian vhost by placing php_admin_value eaccelerator.enable 0 in the vhost section.
Setting this value to "1" enables eAccelerator, which is also the default value. Setting it to "0" will disable eAccelerator.
eaccelerator.enable = "1"
eaccelerator.optimizer
Enables or disables the optimizer which may speed up code execution. Setting it "1" will enable eAccelerator, "0" disables it. By default the optimizer is enabled. The optimizer will only run when the script is compiled before it's cached.
eaccelerator.optimizer = "1"
eaccelerator.debug
Enables or disables debug logging. Setting this to 1 will print information to the log file about the cache hits of a file. This is only useful when debugging eAccelerator for bug reports.
eaccelerator.debug = 0
eaccelerator.log_file
Set the log file for eaccelerator. When this option isn't set then the data will be logged to stderr, when using PHP with Apache these lines will be added to the Apache error log.
eaccelerator.log_file = "/var/log/httpd/eaccelerator_log"
eaccelerator.name_space
When using the user cache api for storing data in shared memory, all keys are prepended by the hostname used for the current request. This hostname equals the ServerName? set in the vhost section of apache. This is done to avoid duplicate keys between vhosts. Sometimes this behaviour is desired to share data between vhosts. When setting this option this namespace is used to prepend to each key. By default this is set to "" which instructs eAccelerator to use the hostname as namespace.
When setting this in the main PHP configuration file this namespace will be used by all vhosts. This value can also be set in the vhost section or even in a .htaccess file to allow sharing of data between only two vhosts.
eaccelerator.name_space = ""
eaccelerator.check_mtime
On every hit eAccelerator will check the modification time of a script to see if it changed and needs to be recompiled. Although this is a lot faster then opening the file and compiling it, this still adds some overhead because a stat call needs to be done every time. This setting allows you to disable this check. The downside of disabling this check is that you need to manually clean the eAccelerator cache when you update a file.
By default this check is enabled.
eaccelerator.check_mtime = "1"
eaccelerator.filter
Determine which PHP files can be cached. You can specify the pattern (for example "*.php *.phtml") the PHP script filename needs to match. If a pattern starts with "!", the files that match that pattern are excluded from the cache. Default value is "" which will cache all scripts PHP compiles.
Please note that eaccelerator.filter doesn't work on a URL basis but rather on the absolute filesystem path, so a filter of !/home* would exclude all scripts in /home from being cached.
Multiple patterns need to be seperated by spaces or tabs, but not commas.
eaccelerator.filter = ""
eaccelerator.shm_max
By default there is no limit on the maximum size a user can put in shared memory w
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