How to install Alternative PHP Cache

What is APC cache?

The Alternative PHP Cache (APC) is a free and open opcode cache for PHP. It was conceived of to provide a free, open, and robust framework for caching and optimizing PHP intermediate code.

Installing

APC Cache is not included with the latest release of php (although it is planned on being included with version 6). It says on the main PHP website that the .dlls can be downloaded from the pecl extensions package, but after downloading and extracting it, I realized that it is not there. I have found the correct .dlls and other files that are needed and they can be download from my server here.

After downloading and extracting the above zip file, complete the following steps:

1) copy the proper php_apc.dll (depending on your version) into your php extensions directory

2) add the following to your php.ini: extension=php_apc.dll (this should be placed under the other extension lines)

3) add the following to your php.ini:

apc.shm_segments=1
apc.optimization=0
apc.shm_size=128
apc.ttl=7200
apc.user_ttl=7200
apc.num_files_hint=1024
apc.mmap_file_mask=/tmp/apc.XXXXXX
apc.enable_cli=1

Note: APC needs a temp path to exist, and be writable by the web server. It checks TMP, TEMP, USERPROFILE environment variables in that order and finally tries the WINDOWS directory if none of those are set.

4) copy apc.php (included with the .zip file) to directory on your web server and launch it.

You should see the following:

APC Cache options

Here is some more information about the various options that can be used to setup apc cache.

apc.enabled This can be set to 0 to disable APC. This is
primarily useful when APC is statically compiled
into PHP, since there is no other way to disable
it (when compiled as a DSO, the zend_extension
line can just be commented-out).
(Default: 1)

apc.shm_segments The number of shared memory segments to allocate
for the compiler cache. If APC is running out of
shared memory but you have already set
apc.shm_size as high as your system allows, you
can try raising this value.
(Default: 1)

apc.shm_size The size of each shared memory segment in MB.
By default, some systems (including most BSD
variants) have very low limits on the size of a
shared memory segment.
(Default: 30)

apc.optimization The optimization level. Zero disables the
optimizer, and higher values use more aggressive
optimizations. Expect very modest speed
improvements. This is experimental.
(Default: 0)

apc.num_files_hint A “hint” about the number of distinct source files
that will be included or requested on your web
server. Set to zero or omit if you’re not sure;
this setting is mainly useful for sites that have
many thousands of source files.
(Default: 1000)

apc.ttl The number of seconds a cache entry is allowed to
idle in a slot in case this cache entry slot is
needed by another entry. Leaving this at zero
means that your cache could potentially fill up
with stale entries while newer entries won’t be
cached.
(Default: 0)

apc.user_ttl The number of seconds a user cache entry is allowed
to idle in a slot in case this cache entry slot is
needed by another entry. Leaving this at zero
means that your cache could potentially fill up
with stale entries while newer entries won’t be
cached.
(Default: 0)

apc.gc_ttl The number of seconds that a cache entry may
remain on the garbage-collection list. This value
provides a failsafe in the event that a server
process dies while executing a cached source file;
if that source file is modified, the memory
allocated for the old version will not be
reclaimed until this TTL reached. Set to zero to
disable this feature.
(Default: 3600)

apc.filters A comma-separated list of POSIX extended regular
expressions. If any pattern matches the source
filename, the file will not be cached. Note that
the filename used for matching is the one passed
to include/require, not the absolute path. If the
first character of the expression is a + then the
expression will be additive in the sense that any
files matched by the expression will be cached, and
if the first character is a – then anything matched
will not be cached. The – case is the default, so
it can be left off.
(Default: “”)

apc.enable_cli Mostly for testing and debugging. Setting this enables APC
for the CLI version of PHP. Normally you wouldn’t want to
create, populate and tear down the APC cache on every CLI
request, but for various test scenarios it is handy to be
able to enable APC for the CLI version of APC easily.
(Default: 0)

apc.max_file_size Prevents large files from being cached.
(Default: 1M)

apc.stat Whether to stat the main script file and the fullpath
includes. If you turn this off you will need to restart
your server in order to update scripts.
(Default: 1)

apc.write_lock On busy servers when you first start up the server, or when
many files are modified, you can end up with all your processes
trying to compile and cache the same files. With write_lock
enabled, only one process at a time will try to compile an
uncached script while the other processes will run uncached
instead of sitting around waiting on a lock.
(Default: 1)

apc.rfc1867 RFC1867 File Upload Progress hook handler is only available
if you compiled APC against PHP 5.2.0 or later. When enabled
any file uploads which includes a field called
APC_UPLOAD_PROGRESS before the file field in an upload form
will cause APC to automatically create an upload_
user cache entry where is the value of the
APC_UPLOAD_PROGRESS form entry.
(Default: 0)

The offical PHP manual page can be found here.