[PHP] DataStore Interface for the Transients API

00-data-store-interface-1.php

<?php
/**
 * A wrapper for the Transients API. Because using `setcookie` only works in the `init`
 * hook of WordPress, then we need a way to simulate it. That's what the purpose of this class
 * does.
 *
 * It will use the ID of the user who is currently logged in (or the PHP's get_current_user value if
 * they are not logged in).
 *
 * @author Tom McFarlin <tom@tommcfarlin.com>
 */
interface DataStore {
	/**
	 * Determines if a transient value already exists identified with the incoming key.
	 *
	 * @param string $key The key used to identify the key in the database.
	 *
	 * @return bool       True if a transient exists; otherwise, false.
	 */
	public function has( string $key );

	/**
	 * Saves the specified value for 24 hours.
	 *
	 * @param string $key   The key used to identify the key in the database.
	 * @param string $value The value to save for 24 hours.
	 */
	public function set( string $key, string $value );

	/**
	 * Retrieves the transient value from the database.
	 *
	 * @param string $key The key used to identify the key in the database.
	 *
	 * @return string     The value associated with the incoming transient.
	 */
	public function get( string $key );

	/**
	 * Deletes the transient data.
	 *
	 * @param string $key The key used to identify the key in the database.
	 */
	public function delete( string $key );
}

00-data-store-interface-2.php

<?php
/**
 * A wrapper for the Transients API. Because using `setcookie` only works in the `init`
 * hook of WordPress, then we need a way to simulate it. That's what the purpose of this class
 * does.
 *
 * It will use the ID of the user who is currently logged in (or the PHP's get_current_user value if
 * they are not logged in).
 *
 * @author Tom McFarlin <tom@tommcfarlin.com>
 */
interface DataStore {

	/**
	 * Determines if a transient value already exists identified with the incoming key.
	 *
	 * @param string $key The key used to identify the key in the database.
	 *
	 * @return bool       True if a transient exists; otherwise, false.
	 */
	public function has(string $key);

	/**
	 * Saves the specified value for 24 hours.
	 *
	 * @param string $key   The key used to identify the key in the database.
	 * @param string $value The value to save for 24 hours.
	 */
	public function set(string $key, string $value);

	/**
	 * Retrieves the transient value from the database.
	 *
	 * @param string $key The key used to identify the key in the database.
	 *
	 * @return string     The value associated with the incoming transient.
	 */
	public function get(string $key);

	/**
	 * Deletes the transient data.
	 *
	 * @param string $key The key used to identify the key in the database.
	 */
	public function delete(string $key);

	/**
	 * Creates a unique key using a combination of the incoming database key and the user's ID.
	 *
	 * @param string $key The key used to store transient data.
	 *
	 * @return string     The unique key used to store values associated with the data store.
	 *
	 */
	private function get_unique_key(string $key);
}

01-data-store.php

<?php

/**
 * Initializes the User ID properly this is what's going to be appended to incoming
 * keys when saving or checking for values.
 *
 * Use PHP's native get_current_user function then fall back to WP's
 * and use that to help generate the key.
 */
public function __construct() 
{
	$this->user_id = get_current_user();
	if (get_current_user_id()) {
		$this->user_id = get_current_user_id();
	}
}

02-get-unique-key.php

<?php

/**
 * Creates a unique key using a combination of the incoming database key and the user's ID.
 *
 * @param string $key The key used to store transient data.
 * @return string     The unique key used to store values associated with the data store.
 */
private function getUniqueKey(string $key) 
{
	return $key .= '-' . $this->user_id;
}