Class

LruCache

A bounded in-memory cache that forgets the least recently used entries first.

Introduction#

Reading an entry (get(), has()) makes it the most recently used; setting one does too.
Past $maxEntries entries, or $maxBytes bytes, the least recently used go first. The bytes are those of each key and of string values; other values count their key only.
An entry with a TTL is gone after that many seconds, by the monotonic clock. Expired entries are dropped when read, and otherwise evicted as the least recently used.
Every operation is O(1): the entries are one PHP array in the order of their last use.

Class synopsis#

final class LruCache implements \Countable {
    /* Methods */
    public LruCache::__construct(int $maxEntries = PHP_INT_MAX, int $maxBytes = PHP_INT_MAX)
    public LruCache::get(string $key, mixed $default = null): mixed
    public LruCache::has(string $key): bool
    public LruCache::set(string $key, mixed $value, ?float $ttl = null): bool
    public LruCache::delete(string $key): bool
    public LruCache::clear(): void
    public LruCache::count(): int
    public LruCache::bytes(): int
}

Methods#

Method	Description
`__construct`	Creates an empty cache.
`get`	Returns the value stored under `$key`, and makes it the most recently used.
`has`	Returns whether there is an entry for `$key`, and makes it the most recently used if there is.
`set`	Stores `$value` under `$key`, making room as needed.
`delete`	Whether there was an entry for $key.
`clear`	Removes every entry.
`count`	The entries held, expired ones not yet dropped included.
`bytes`	The bytes held, when $maxBytes is set.

Examples#

Example 1

$cache = new LruCache(maxEntries: 10_000, maxBytes: 64 << 20);
$cache->set('user:42', $json, ttl: 60);
$json = $cache->get('user:42');   // null once expired or evicted

Used in#

Caching: memoizationA cache of a pure function can be shared by every request, if it is bounded.