一、PHP加速器介绍
PHP加速器是一个为了提高PHP执行效率，从而缓存起PHP的操作码，这样PHP后面执行就不用解析转换了，可以直接调用PHP操作码，这样速度上就提高了不少。
Apache中使用mod_php的请求、响应执行流程：
1、Apache接收请求。
2、Apache传递请求给mod_php。
3、mod_php定位磁盘文件，并加载到内存中。
4、mod_php编译源代码成为opcode树。
5、mod_php执行opcode树。
PHP加速器相应的就是第四步，它的目的就是防止PHP每次请求都重复编译PHP代码，因为在高访问量的网站上，大量的编译往往没有执行速度快呢？所以这里面有个瓶颈就是PHP的重复编译既影响了速度又加载了服务器负载，为了解决此问题，PHP加速器就这样诞生了。
二、PHP加速器安装与配置
1、安装配置APC
APC全称是Alternative PHP Cache,官方翻译叫”可选PHP缓存”,它是PHP PECL中的一个扩展，好像是facebook在使用它，下面开始安装(ubuntu环境)：
$wget http://pecl.php.net/get/APC-3.0.19.tgz
$tar xvzf APC-3.0.19.tgz
$cd APC-3.0.19/APC-3.0.19
$/usr/local/php/bin/phpize
$./configure –enable-apc –enable-apc-mmap –with-php-config=/usr/local/php/bin/php-config
$make
$sudo make install
下面我们再配置APC,因为我的PECL扩展路径改变了，所以我得移动下编译好的文件：
$sudo mv /usr/local/php/lib/php/extensions/no-debug-non-zts-20060613/apc.so /usr/local/php/lib/php/extensions/PECL
然后我们再编辑php.ini文件进行配置，请把下面的代码加入到php.ini中即可：
extension_dir = "/usr/local/php/lib/php/extensions/PECL"
extension = apc.so
; APC
apc.enabled = 1
apc.shm_segments = 1
apc.shm_size = 64
apc.optimization = 1
apc.num_files_hint = 0
apc.ttl = 0
apc.gc_ttl = 3600
apc.cache_by_default = on
这样重启apache就会在phpinfo()信息中显示。
使用php apc模块需要注意的几点
在maillist中看到Rasmus的一段对于php APC模块的发言。作为APC的作者，他的见解应该是很有参考价值的。
Php代码
APC will probably be 20-30% faster, but if you are writing to it frequently it can cause problems. The APC cache is best for things that change very rarely. And by very rarely I mean days, not hours or minutes. Because of the way APC does an anonymous file-backed mmap where I unlink the file at startup to get process-death protection, it isn’t easy to get at the cache from a separate standalone command line script. That can be solved by mmap’ing slightly differently, but in the default config your approach won’t work. -Rasmus
就是说APC不适合用于频繁写的场合，你最好只用它来保存那种几天都不会更改的内容。否则出了莫名其妙的问题就不好怎么解释了。
在以前的应用中，我确实有将apc用在频繁写的场合，偶尔会出现内存耗尽，进而引起所有http请求卡死，形式一发不可收拾整个服务器当掉。所以现在我仅仅用apc来缓存opcode的php代码，不在程序中显式的调用它，算是相安无事。
2、安装配置eAccelerator
eAccelerator的前身其实是truck-mmcache，因为开发truk-mmcache的人被Zend给招安了，所以开发eAccelerator的人继承了truk-mmcache的一些特性，设计出eAccelerator加速器。安装如下：
$wget http://jaist.dl.sourceforge.net/sourceforge/eaccelerator/eaccelerator-0.9.5.tar.bz2
$tar -jxf eaccelerator-0.9.5.tar.bz2
$cd eaccelerator-0.9.5
$/usr/local/php/bin/phpize
$./configure –enable-eaccelerator=shared –with-php-config=/usr/local/php/bin/php-config
$make
$sudo make install
$sudo mv /usr/local/php/lib/php/extensions/no-debug-non-zts-20060613/eaccelerator.so /usr/local/php/lib/php/extensions/PECL
将下面代码加入php.ini文件中
extension = eaccelerator.so
; eAccelerator
eaccelerator.shm_size = "16"
eaccelerator.cache_dir = "/tmp/eaccelerator"
eaccelerator.enable = "1"
eaccelerator.optimizer = "1"
eaccelerator.check_mtime = "1"
eaccelerator.debug = "0"
eaccelerator.filter = ""
eaccelerator.shm_max = "0"
eaccelerator.shm_ttl = "0"
eaccelerator.prune_period = "0"
eaccelerator.shm_only = "0"
eaccelerator.compress = "1"
eaccelerator.compress_level = "9"
创建缓存目录,重启apache
$sudo mkdir /tmp/eaccelerator
$sudo chmod 777 /tmp/eaccelerator
$sudo /usr/local/apache/apachectl restart
在phpinfo()检查是否安装成功.
3、安装配置XCache
XCache作为国人自己开发的东西，做小菜鸟的我也感到骄傲，而且XCache无论在速度还是性能上都做的不错。下面就赶紧让我们品尝它吧！
$wget http://xcache.lighttpd.net/pub/Releases/1.2.2/xcache-1.2.2.tar.gz
$tar xvzf xcache-1.2.2.tar.gz
$cd xcache-1.2.2
$/usr/local/php/bin/phpize
$./configure –enable-xcache –enable-xcache-coverager –with-php-config=/usr/local/php/php-config
$make
$sudo make install
$sudo mv /usr/local/php/lib/php/extensions/no-debug-non-zts-20060613/xcache.so /usr/local/php/lib/php/extensions/PECL
在php.ini添加配置信息：
extension = xcache.so
; xcache
xcache.admin.user = "admin"
xcache.admin.pass = "(执行) echo ’(你的密码)’|md5sum(得出的密文)"
;
xcache.size = 24M
xcache.shm_scheme = "mmap"
xcache.count = 2
xcache.slots = 8k
xcache.ttl = 0
xcache.gc_interval = 0
xcache.var_size = 8M
xcache.var_count = 1
xcache.var_slots = 8k
xcache.var_ttl = 0
xcache.var_maxttl = 0
xcache.var_gc_interval = 300
xcache.test = Off
xcache.readonly_protection = On
xcache.mmap_path = "/tmp/xcache"
xcache.coredump_directory = ""
xcache.cacher = On
xcache.stat = On
xcache.optimizer = Off
;
xcache.coverager = On
xcache.coveragedump_directory = ""
创建缓存目录，重启apache
$sudo mkdir /tmp/xcache
$sudo chmod 777 /tmp/xcache
$sudo /usr/local/apache/bin/apachectl restart
去查看phpinfo()信息吧！
三、PHP加速器测试
1、测试环境
硬件: AMD Athlon 64 X2 Dual Core Processor 4400+ @ 2.2GHz CPU, 2GB 内存. 160GB SATA 硬盘
软件: Linux Ubuntu server Gutsy 7.10, Apache 2.2.4, MySQL 5.0.45 和 PHP 5.2.3
测试指令: ab -c5 -n3000 http://example.com/ (我们使用的是Apache Benchmark (ab) 工具，并发连接为5，3000次请求)
2、测试结果
无任何加速器:
Document Path: /
Document Length: 21757 bytes
Concurrency Level: 5
Time taken for tests: 288.255212 seconds
Complete requests: 3000
Failed requests: 0
Write errors: 0
Total transferred: 66777000 bytes
HTML transferred: 65271000 bytes
Requests per second: 10.41 [#/sec] (mean)
Time per request: 480.425 [ms] (mean)
Time per request: 96.085 [ms] (mean, across all concurrent requests)
Transfer rate: 226.23 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 0 0.5 0 19
Processing: 181 479 186.0 444 1822
Waiting: 166 461 184.7 427 1708
Total: 181 479 186.0 444 1822
Percentage of the requests served within a certain time (ms)
50% 444
66% 525
75% 577
80% 619
90% 732
95% 819
98% 946
99% 1012
100% 1822 (longest request)
APC加速器:
Document Path: /
Document Length: 21757 bytes
Concurrency Level: 5
Time taken for tests: 98.530068 seconds
Complete requests: 3000
Failed requests: 0
Write errors: 0
Total transferred: 66777000 bytes
HTML transferred: 65271000 bytes
Requests per second: 30.45 [#/sec] (mean)
Time per request: 164.217 [ms] (mean)
Time per request: 32.843 [ms] (mean, across all concurrent requests)
Transfer rate: 661.84 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 0 0.0 0 2
Processing: 58 163 71.2 155 2452
Waiting: 53 158 69.6 150 2329
Total: 58 163 71.2 155 2452
Percentage of the requests served within a certain time (ms)
50% 155
66% 178
75% 193
80% 204
90% 235
95% 258
98% 285
99% 302
100% 2452 (longest request)
eAccelerator加速器:
Document Path: /
Document Length: 21757 bytes
Concurrency Level: 5
Time taken for tests: 95.983986 seconds
Complete requests: 3000
Failed requests: 0
Write errors: 0
Total transferred: 66777000 bytes
HTML transferred: 65271000 bytes
Requests per second: 31.26 [#/sec] (mean)
Time per request: 159.973 [ms] (mean)
Time per request: 31.995 [ms] (mean, across all concurrent requests)
Transfer rate: 679.39 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 0 0.1 0 3
Processing: 57 159 91.3 148 3830
Waiting: 50 152 89.8 142 3704
Total: 57 159 91.3 148 3830
Percentage of the requests served within a certain time (ms)
50% 148
66% 174
75% 193
80% 205
90% 239
95% 263
98% 289
99% 309
100% 3830 (longest request)
XCache加速器:
Document Path: /
Document Length: 21757 bytes
Concurrency Level: 5
Time taken for tests: 99.76300 seconds
Complete requests: 3000
Failed requests: 0
Write errors: 0
Total transferred: 66777000 bytes
HTML transferred: 65271000 bytes
Requests per second: 30.28 [#/sec] (mean)
Time per request: 165.127 [ms] (mean)
Time per request: 33.025 [ms] (mean, across all concurrent requests)
Transfer rate: 658.19 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 0 0.0 0 2
Processing: 59 164 83.4 155 3367
Waiting: 52 156 66.4 148 1802
Total: 59 164 83.4 155 3367
Percentage of the requests served within a certain time (ms)
50% 155
66% 178
75% 196
80% 206
90% 237
95% 263
98% 287
99% 305
100% 3367 (longest request)
3、结果摘要
请求时间(秒)
单次请求时间(毫秒)
最大内存占用(MB)
最小内存占用(MB)
None
10.41
96.08
24
24
APC
30.45
32.84
21
21
eAccelerator
31.26
31.99
23
18
XCache
30.28
33.02
29
19
四、PHP加速器比较结果总结
1、通过测试得出eAccelerator在请求时间和内存占用综合方面是最好的。
2、通过测试得出使用加速器比无加速器在请求时间快了3倍左右。
3、通过各个官方观察，XCache是更新最快的，这也说明最有发展的。
以上是总结结果，你也许会问我到底用那个加速器好呢？我只能告诉你，首先，用一定比不用好，其次每个加速器还有一些可以调优的参数，所以要根据你的系统环境而定，然后，我个人觉得你可以详细研究下eAccelerator和XCache，这两款潜力还是很大的。
