jdorn/file-system-cache

an easy way to cache data in the file system

dev-master / 1.0.x-dev 2013-07-05 13:28 UTC

Requires

• php: >=5.3.0

LGPL

• Jeremy Dorn

• cache
• file system

README

A simple PHP class for caching data in the filesystem. Major features include:

• Support for TTL when storing data
• Support for "Newer Than" parameter when retrieving data
• Every call is an atomic operation with proper file locking
• Can group cache keys together for easy invalidation
• Composer support
• PHPUnit tests

Getting Started

FileSystemCache can be installed with Composer or downloaded manually.

With Composer

If you're already using Composer, just add jdorn/file-system-cache to your composer.json file. FileSystemCache works with Composer's autoloader out of the bat.

{
	"require": {
		"jdorn/file-system-cache": "dev-master"
	}
}

Manually

If you aren't using Composer, you just need to include lib/FileSystemCache.php in your script.

require_once("path/to/FileSystemCache.php");

Setting the Cache Directory

By default, all cached data is stored in the cache directory relative to the currently executing script. You can change this by setting the $cacheDir static property.

<?php
FileSystemCache::$cacheDir = '/tmp/cache';

FileSystemCache needs write access to the cache directory.
It's easiest if Apache (or whatever web server you're using) owns the directory.

Cache Keys

All of FileSystemCache's methods operate on Cache Keys. There is a generateCacheKey method that returns a Cache Key object.

You can pass in almost anything as the key data (array, object, string, number). Any non-strings will be serialized and hashed.

<?php
//array of data
$key_data = array(
	'user_id'=>1001,
	'ip address'=>'10.1.1.1'
);

//string
$key_data = 'my_key';

//object
$key_data = new SomeObject();

//number
$key_data = 1005;


//generate a key object
$key = FileSystemCache::generateCacheKey($key_data);

You can group cache keys together to better organize your data and make invalidation easier.

<?php
$key_data = 'my_key';

//store in root directory (same as leaving out second parameter)
$key = FileSystemCache::generateCacheKey($key_data, null);

//store in 'group1' directory
$key = FileSystemCache::generateCacheKey($key_data, 'group1');

//store in 'group1/subgroup' directory
$key = FileSystemCache::generateCacheKey($key_data, 'group1/subgroup');

The resulting file structure will look like:

$cacheDir/
| +- my_key.cache
| +- group1/
|    | +- my_key.cache
|    | +- subgroup/
|    |    | +- my_key.cache

Store

Data is serialized before storing, so you can use strings, array, objects, or numbers.

$data = array(
	'this'=>'is some data I want to cache',
	'it'=>'can be a string, array, object, or number.'
);

$key = FileSystemCache::generateCacheKey('mykey');

FileSystemCache::store($key, $data);

If you want the data to expire automatically after a set amount of time, use the optional ttl parameter.

// Expire automatically after 1 hour (3600 seconds)
FileSystemCache::store($key, $data, 3600);

Retrieve

You retrieve data using the same cache key you used to store it. False will be returned if the data was not cached or expired.

$data = FileSystemCache::retrieve($key);

// If there was a cache miss
if($data === false) {
	...
}

You can specify a newer than timestamp to only retrieve cached data that was stored after a certain time. This is useful for storing a compiled version of a source file.

$file = 'source_file.txt';
$modified = filemtime($file);

$key = FileSystemCache::generateCacheKey($file);

$data = FileSystemCache::retrieve($key, $modified);

// If there was a cache miss
if($data === false) {
	...
}

Get and Modify

There is an atomic Get and Modify method as well.

FileSystemCache::getAndModify($key, function($value) {
	$value->count++;
	
	return $value;
});

If the data was originally cached with a TTL, you can pass true as the 3rd parameter to resset the TTL.
Otherwise, it will be based on the original time it was stored.

Invalidate

You can invalidate a single cache key or a group of cache keys.

FileSystemCache::invalidate($key);

FileSystemCache::invalidateGroup('mygroup');

Invalidating a group is done recursively by default and all sub-groups will also be invalidated. If you pass false as the 2nd parameter, you can make it non-recursive.

FileSystemCache::invalidateGroup('mygroup', false);

Running the Tests

You need PHPUnit installed to run the tests. Configuration is defined in phpunit.xml.dist. Running the tests is easy:

phpunit