Optimize PHP programs using APC cache_PHP tutorial

Alternative PHP Cache（APC）是 PHP 的一个免费公开的优化代码缓存。它用来提供免费，公开并且强健的架构来缓存和优化 PHP 的中间代码。

APC 官方网站为http://pecl.php.net/package/apc

Windows下的拓展模块下载地址http://www.sitebuddy.com/php/accelerators/apc_windows_binaries_builds

在 Windows 下，APC 要求有 c: mp 目录，并且该目录要对 Web 服务器进程可写。

1、安装

以PHP extension 形式安装

2、配置

apc.enabled        boolean

apc.optimization   optimization

选项在脚本中可以改变

APC PHP.ini配置选项详解

[APC]

; Alternative PHP Cache 用于缓存和优化PHP中间代码

apc.cache_by_default = On

;SYS

; 是否默认对所有文件启用缓冲。

; 若设为Off并与以加号开头的apc.filters指令一起用，则文件仅在匹配过滤器时才被缓存。

apc.enable_cli = Off

;SYS

; 是否为CLI版本启用APC功能，仅用于测试和调试目的才打开此指令。

apc.enabled = On

; 是否启用APC，如果APC被静态编译进PHP又想禁用它，这是唯一的办法。

apc.file_update_protection = 2

;SYS

; 当你在一个运行中的服务器上修改文件时，你应当执行原子操作。

; 也就是先写进一个临时文件，然后将该文件重命名(mv)到最终的名字。

; 文本编辑器以及 cp, tar 等程序却并不是这样操作的，从而导致有可能缓冲了残缺的文件。

; 默认值 2 表示在访问文件时如果发现修改时间距离访问时间小于 2 秒则不做缓冲。

; 那个不幸的访问者可能得到残缺的内容，但是这种坏影响却不会通过缓存扩大化。

; 如果你能确保所有的更新操作都是原子操作，那么可以用 0 关闭此特性。

; 如果你的系统由于大量的IO操作导致更新缓慢，你就需要增大此值。

apc.filters =

;SYS

; 一个以逗号分隔的POSIX扩展正则表达式列表。

; 如果源文件名与任意一个模式匹配，则该文件不被缓存。

; 注意，用来匹配的文件名是传递给include/require的文件名，而不是绝对路径。

; 如果正则表达式的第一个字符是"+"则意味着任何匹配表达式的文件会被缓存，

; 如果第一个字符是"-"则任何匹配项都不会被缓存。"-"是默认值，可以省略掉。

apc.ttl = 0

;SYS

; 缓存条目在缓冲区中允许逗留的秒数。0 表示永不超时。建议值为7200~36000。

; 设为 0 意味着缓冲区有可能被旧的缓存条目填满，从而导致无法缓存新条目。

apc.user_ttl = 0

;SYS

; 类似于apc.ttl，只是针对每个用户而言，建议值为7200~36000。

; 设为 0 意味着缓冲区有可能被旧的缓存条目填满，从而导致无法缓存新条目。

apc.gc_ttl = 3600

;SYS

; 缓存条目在垃圾回收表中能够存在的秒数。

; 此值提供了一个安全措施，即使一个服务器进程在执行缓存的源文件时崩溃，

; 而且该源文件已经被修改，为旧版本分配的内存也不会被回收，直到达到此TTL值为止。

; 设为零将禁用此特性。

apc.include_once_override = Off

;SYS

; 请保持为Off，否则可能导致意想不到的结果。

apc.max_file_size = 1M

;SYS

; 禁止大于此尺寸的文件被缓存。

apc.mmap_file_mask =

;SYS

; 如果使用–enable-mmap(默认启用)为APC编译了MMAP支持，

; 这里的值就是传递给mmap模块的mktemp风格的文件掩码(建议值为"/tmp/apc.XXXXXX")。

; 该掩码用于决定内存映射区域是否要被file-backed或者shared memory backed。

; 对于直接的file-backed内存映射，要设置成"/tmp/apc.XXXXXX"的样子(恰好6个X)。

; 要使用POSIX风格的shm_open/mmap就需要设置成"/apc.shm.XXXXXX"的样子。

; 你还可以设为"/dev/zero"来为匿名映射的内存使用内核的"/dev/zero"接口。

; 不定义此指令则表示强制使用匿名映射。

apc.num_files_hint = 1000

;SYS

; Web服务器上可能被包含或被请求的不同源文件的大致数量(建议值为1024~4096)。

; 如果你不能确定，则设为 0 ；此设定主要用于拥有数千个源文件的站点。

apc.optimization = 0

; 优化级别(建议值为 0 ) 。

; 正整数值表示启用优化器，值越高则使用越激进的优化。

; 更高的值可能有非常有限的速度提升，但目前尚在试验中。

apc.report_autofilter = Off

;SYS

; Whether to record all scripts that are automatically not cached due to early/late binding reasons.

apc.shm_segments = 1

;SYS

; The number of shared memory blocks allocated for the compiler buffer (recommended value is 1).

; If APC runs out of shared memory and the apc.shm_size directive has been set to the maximum allowed by the system,

; You can try increasing this value.

apc.shm_size = 30

;SYS

; The size of each shared memory block (in MB, the recommended value is 128~256).

; Some systems (including most BSD variants) have a very small default shared memory block size.

apc.slam_defense = 0

;SYS (It is against the use of this command, it is recommended to use the apc.write_lock command)

; On a very busy server, whether starting a service or modifying a file,

; can cause a race condition due to multiple processes trying to cache a file at the same time.

; This directive is used to set the percentage of the process that skips the caching step when processing uncached files.

; For example, setting it to 75 means that there is a 75% probability of not caching when an uncached file is encountered, thereby reducing the chance of collision.

; It is encouraged to set to 0 to disable this feature.

apc.stat = On

;SYS

; Whether to enable script update checking.

; Be very careful when changing this command value.

; The default value On means that APC checks whether the script has been updated every time it is requested,

; Automatically recompile and cache the compiled content if updated. However, doing so has a negative impact on performance.

; If set to Off, no checking is performed, thus greatly improving performance.

; But in order for the updated content to take effect, you must restart the web server.

; This directive is also valid for include/require files. But it should be noted that

; If you use relative paths, APC must check to locate the file every include/require.

; Using absolute paths can skip the check, so you are encouraged to use absolute paths for include/require operations.

apc.user_entries_hint = 100

;SYS

; Similar to the num_files_hint directive, but for each different user.

; Set to 0 if you are not sure.

apc.write_lock = On

;SYS

; Whether to enable write lock.

; On a very busy server, whether starting a service or modifying a file,

; can cause a race condition due to multiple processes trying to cache a file at the same time.

; Enabling this directive can avoid race conditions.

apc.rfc1867 = Off

;SYS

; After turning on this command, for each uploaded file that contains the APC_UPLOAD_PROGRESS field just before the file field,

; APC will automatically create a user cache entry for upload_ (that is, the APC_UPLOAD_PROGRESS field value).

3. Function

apc_cache_info - Retrieves cached information (and meta-data) from APCs data store
apc_clear_cache - Clears the APC cache
apc_define_constants - Defines a set of constants for later retrieval and mass-definition
apc_delete - Removes a stored variable from the cache
apc_fetch - Fetch a stored variable from the cache
apc_load_constants - Loads a set of constants from the cache
apc_sma_info - Retrieves APCs Shared Memory Allocation information
apc_store - Cache a variable in the data store

The usage of apc is relatively simple, with only a few functions, listed below.

apc_cache_info () returns cache information

apc_clear_cache() clears the apc cache content.

By default (no parameters), only the system cache is cleared. To clear the user cache, the ‘user’ parameter is required.

apc_define_constants (string key, array constants [, bool case_sensitive]) Add array constants to the cache as constants.

apc_load_constants (string Key).

Remove constant cache.

apc_store ( string key, mixed var [, int ttl] ).

Save data in cache.

apc_fetch (string key).

Get the cache content saved by apc_store

apc_delete (string key).

Delete the content saved by apc_store.

apc management:

Go to pecl.php.net to download the apc source code package. There is apc.php, copy it to a place where your web server can access it, and browse to access it.

Management interface functions include:

1. Refresh Data

2. View Host Stats

3. System Cache Entries

4. User Cache Entries

5. Version Check