How much do you know about php apc?

apc definition: apc is an open and free php opcode cache. Its goal is to provide a free, open and sound framework for caching and optimizing PHP intermediate code.

1. apc commonly used functions: 1.apc_clear_cache() clears the apc cache content 2.apc_define_constants(string key,array constants,[,bool case_sensitive]) adds array constants to the cache as constants 3.apc_load_constants(string key) takes out the constant cache 4.apc_store(string key,mixed var [, int ttl]) save data in cache 5.apc_fetch(string key) gets the cache data saved by apc_store 6.apc_delete(string key) deletes the content saved by apc_store 7.apc_add(string key,mixd var [, int ttl]) caches a variable to data storage (only when the variable has not been stored before) 8.apc_exists(mix keys) checks whether one or more apc key names exist 9.apc_delete_file(mixed keys) deletes the cache of a given file from the opcode cache 10.apc_compile_file(string filename [,bool atmic=true]) bypasses the restrictions of filters and caches files 11.apc_cache_info(string cache_type [,bool limited=false]) Get cache i-type milkshake Note: apc_clear_cache only clears the opcode cache file, apc_delete clears the variables in the cache; for predefined variables, you can use the apc_define_constants function; for PHP variables, you can use the function apc_store. It is better to use apc than memcache, and does not need to go through the network transmission protocol tcp; apc does not It is suitable for caching frequently changed user data through the function apc_store. Some strange phenomena will occur; apc itself does not support distribution.

2. apc common configuration: 1. How much memory will be allocated to apc, ini option apc.shm_size (integer) controls this setting. The default is 30M 2. Whether to check file modifications every time apc is requested. The ini option apc.stat controls this setting. The default value is 1, which means that every time a script is requested, whether the script is updated. If updated, the compiled content will be automatically recompiled and cached. , has a proportional impact on performance, so this is set to 0 3.Cache less scripts via ini option apc.filters

3. Advantages of apc: 1. Use spinlocks (spin) lock mechanism to achieve the best performance 2.apc provides apc.php for monitoring and managing apc cache. (Note: Change administrator name and password) 3.apc creates shared memory through mmap anonymous mapping by default, and cache objects are stored in this large memory space. The shared memory is managed by apc itself 4. Adjust the values ​​of apc.shm_size, apc.num_files_hints, apc.user_entires_hint to the best 5.php predefined constants, you can use apc _define——constants() function. However, apc developers say that pecl hidef has better performance and abandons define, which is inefficient. 6.apc_store, for PHP variables such as system settings, the life cycle is the entire application (from the httpd daemon to the shutdown of the httpd daemon), using apc is better than memcache. (No need to go through network transmission protocol) 7.apc is not suitable for frequently changing user data cached through the function apc_store(), and some strange phenomena will occur.

Example:

<?php
/**
*php apc示例
* by http://bbs.it-home.org
*/
$constants = array('APC_FILE'=>'apc.php','AUTHOR'=>'tim');
apc_define_constants('memb',$constants );
apc_load_constants('memb');
//echo APC_FILE;
//echo AUTHOR;
 
if(!apc_fetch('time1')) apc_store('time1',time());
if(!apc_fetch('time2')) apc_store('time2',time(),2);
//echo apc_fetch('time1');
//echo apc_fetch('time2');
 
class a{
     public function b(){echo 'success';}
}
apc_store('obj',new a());
$a = apc_fetch('obj');
//$a-b();
 
$ret = apc_exists(array('foo', 'donotexist', 'bar'));
//array(2) { ["foo"]=> bool(true) ["bar"]=> bool(true) }
?>

Attached, detailed configuration instructions: apc.cache_by_default = on ;sys ; Whether to enable buffering by default for all files. ; If set to off and used with the apc.filters directive starting with a plus sign, files will only be cached if they match the filter. apc.enable_cli = off ;sys ; Whether to enable apc functionality for cli version, turn this directive on only for testing and debugging purposes. apc.enabled = on ; Whether to enable apc. If apc is statically compiled into php and you want to disable it, this is the only way. apc.file_update_protection = 2 ;sys ; When you modify files on a running server, you should perform atomic operations. ; That is, first write to a temporary file, and then rename (mv) the file to the final name. ; Text editors and programs such as cp and tar do not operate in this way, resulting in the possibility of buffering incomplete files. ; The default value 2 means that when accessing a file, if the modification time is found to be less than 2 seconds from the access time, no buffering will be performed. ; The unlucky visitor may get corrupted content, but the bad effect is not amplified by caching. ; If you can ensure that all update operations are atomic, you can turn off this feature with 0. ; If your system updates slowly due to heavy IO operations, you may need to increase this value. apc.filters = ;sys ; A comma-separated list of POSIX extended regular expressions. ; If the source file name matches any of the patterns, the file is not cached. ; Note that the file name used for matching is the file name passed to include/require, not the absolute path. ; If the first character of the regular expression is "+" it means that any files matching the expression will be cached, ; If the first character is "-" then any matches will not be cached. "-" is the default value and can be omitted. apc.ttl = 0 ;sys ; The number of seconds a cache entry is allowed to stay in the buffer. 0 means never times out. The recommended value is 7200~36000. ; Setting to 0 means that the buffer may become filled with old cache entries, preventing new entries from being cached. apc.user_ttl = 0 ;sys ; Similar to apc.ttl, but for each user, the recommended value is 7200~36000. ; Setting to 0 means that the buffer may become filled with old cache entries, preventing new entries from being cached. apc.gc_ttl = 3600 ;sys ; The number of seconds a cache entry can exist in the garbage collection table. ; This value provides a safety measure even if a server process crashes while executing a cached source file, ; and the source file has been modified, the memory allocated for the old version will not be reclaimed until this ttl value is reached. ; Set to zero to disable this feature. apc.include_once_override = off ;sys ; There is currently no documentation for this command, see: http://pecl.php.net/bugs/bug.php?id=8754 ; Please keep it off, otherwise it may cause unexpected results. apc.max_file_size = 1m ;sys ; Prevent files larger than this size from being cached. apc.mmap_file_mask = ;sys ; If mmap support is compiled for apc using --enable-mmap (enabled by default), ; The value here is the mktemp-style file mask passed to the mmap module (the recommended value is "/tmp/apc.xxxxxx"). ; This mask is used to determine whether the memory mapped area should be file-backed or shared memory backed. ; For direct file-backed memory mapping, set it to "/tmp/apc.xxxxxx" (exactly 6 x's). ; To use posix-style shm_open/mmap, it needs to be set to "/apc.shm.xxxxxx". ; You can also set to "/dev/zero" to use the kernel's "/dev/zero" interface for anonymously mapped memory. ; Not defining this directive forces the use of anonymous mapping. apc.num_files_hint = 1000 ;sys ; The approximate number of different source files that may be included or requested on the web server (recommended value is 1024~4096). ; If you are not sure, set to 0; This setting is mainly used for sites with thousands of source files. apc.optimization = 0 ; Optimization level (recommended value is 0). ; A positive integer value enables the optimizer, with higher values ​​using more aggressive optimizations. ; Higher values ​​may have very limited speed improvements, but are currently experimental. 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 has exhausted 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 at which the process 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. ; Encouraged to be set to 0 to disable this feature. apc.stat = on ;sys ; Whether to enable script update checking. ; Be very careful when changing this directive 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. ; If you are not sure, set to 0. 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. ; Enable this directive to avoid race conditions. apc.rfc1867 = off ;sys ; After turning on this directive, 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_ (which is the apc_upload_progress field value).