### PSR-16 Simple Cache Interfaces

Source: https://github.com/php-fig/simple-cache/blob/master/README.md

This package defines the interfaces for PSR-16 Simple Cache, a standard for cache implementations in PHP. It does not provide an actual cache but rather the contract that cache implementations must adhere to.

```php
<?php

namespace Psr\SimpleCache;

/**
 * Represents a cache item that can be stored in a cache.
 */
interface CacheItemInterface
{
    /**
     * Get the key of the cached value.
     *
     * @return string
     *   The key that the cache item is stored under.
     */
    public function getKey(): string;

    /**
     * Get the value of the cached item.
     *
     * @return mixed
     *   The value that was stored in the cache.
     */
    public function get(): mixed;

    /**
     * Return whether the value is hit in the cache because it exists.
     *
     * @return bool
     *   True if the value exists in the cache, false otherwise.
     */
    public function isHit(): bool;

    /**
     * Set the value of the cached item.
     *
     * @param mixed $value
     *   The value to store in the cache.
     *
     * @return static
     *   The object instance.
     */
    public function set(mixed $value): static;

    /**
     * Get the expiration timestamp of the item.
     *
     * @return DateTimeInterface|null
     *   The expiration timestamp.
     */
    public function getExpiresAt(): ?DateTimeInterface;

    /**
     * Set the expiration timestamp of the item.
     *
     * @param DateInterval|DateTimeInterface|null $time
     *   The expiration timestamp.
     *
     * @return static
     *   The object instance.
     */
    public function expiresAt(?DateTimeInterface $time): static;

    /**
     * Set the expiration time with the given TTL.
     *
     * @param DateInterval|int|null $time
     *   The TTL interval.
     *
     * @return static
     *   The object instance.
     */
    public function expiresAfter(DateInterval|int|null $time): static;
}

```

```php
<?php

namespace Psr\SimpleCache;

/**
 * Simple cache interface.
 */
interface CacheInterface
{
    /**
     * Fetches a value from the cache.
     *
     * @param string $key     A unique key of the item in the cache.
     * @param mixed  $default Default value to return if the key does not exist.
     *
     * @return mixed The value of the key in the cache, or $default if not found.
     *
     * @throws PsrSimpleCacheInvalidArgumentException
     *   If the $key is not a valid value for a key.
     */
    public function get(string $key, mixed $default = null): mixed;

    /**
     * Persists a value in the cache.
     *
     * @param string              $key   The key of the item to store.
     * @param mixed               $value The value to store.
     * @param DateInterval|int|null $ttl   The TTL value, a DateInterval object or null for no expiration.
     *
     * @return bool True if the value was successfully stored, false otherwise.
     *
     * @throws PsrSimpleCacheInvalidArgumentException
     *   If the $key is not a valid value for a key.
     */
    public function set(string $key, mixed $value, DateInterval|int|null $ttl = null): bool;

    /**
     * Delete a value from the cache.
     *
     * @param string $key The key of the item to delete.
     *
     * @return bool True if the value was successfully deleted, false otherwise.
     *
     * @throws PsrSimpleCacheInvalidArgumentException
     *   If the $key is not a valid value for a key.
     */
    public function delete(string $key): bool;

    /**
     * Erase all values from the cache.
     *
     * @return bool True if the cache was successfully cleared, false otherwise.
     */
    public function clear(): bool;

    /**
     * Delete multiple values from the cache.
     *
     * @param iterable<string> $keys A list of keys to delete.
     *
     * @return bool True if the value was successfully deleted, false otherwise.
     *
     * @throws PsrSimpleCacheInvalidArgumentException
     *   If the $keys are not a valid value for a key.
     */
    public function deleteMultiple(iterable $keys): bool;

    /**
     * Set multiple key/value pairs in the cache.
     *
     * @param iterable<string, mixed> $values A dictionary of key/value pairs.
     * @param DateInterval|int|null     $ttl    The TTL value, a DateInterval object or null for no expiration.
     *
     * @return bool True if the values were successfully stored, false otherwise.
     *
     * @throws PsrSimpleCacheInvalidArgumentException
     *   If any of the $keys are not a valid value for a key.
     */
    public function setMultiple(iterable $values, DateInterval|int|null $ttl = null): bool;

    /**
     * Get multiple key/value pairs from the cache.
     *
     * @param iterable<string> $keys  A list of keys to retrieve.
     * @param mixed             $default Default value to return for keys that do not exist.
     *
     * @return iterable<string, mixed>
     *   A dictionary of key/value pairs.
     *
     * @throws PsrSimpleCacheInvalidArgumentException
     *   If any of the $keys are not a valid value for a key.
     */
    public function getMultiple(iterable $keys, mixed $default = null): iterable;
}

```

```php
<?php

namespace Psr\SimpleCache;

/**
 * Exception thrown when a cache key is invalid.
 */
class InvalidArgumentException extends ExceptionInvalidArgumentException
{
}

```

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