An abstract class to facilitate working with WordPress transients

wp_transients_helper.php

<?php
abstract class av_transients_helper{
	var $transient_name;
	var $expire;
	function __construct($id, $expire){
		$this->transient_name = $id;
		$_expire = ( (int)$expire > 0 ) ? (int)$expire : 1;
		$this->transient_expire = 60 * 60 * $_expire;
	}
	public function get_data(){
		$_transient_data = $this->get_transient();
		if ( $_transient_data )
			return $_transient_data;
		else
			return $this->refresh_data();
	}
	private function get_transient(){
		$_transient = get_transient($this->transient_name);
		if ( $_transient )
			return maybe_unserialize($_transient);
		else
			return false;
	}	
	private function refresh_data(){
		$raw = $this->get_external_data();
		if ( $raw ) return $this->set_transient($raw);
		else return false;
	}
	/**
	 * Get data from external API
	 * @uses WP_Http WordPress HTTP request class
	 * @return Raw API Data; false on failure
	 **/
	private function get_external_data(){
		if ( !class_exists( 'WP_Http') ) require_once( ABSPATH . WPINC . '/class-http.php' );
		$request = new WP_Http;
		$request_url = $this->build_request_url();
		$result = $request->request($request_url);
		if ( is_array($result['response']) && $result['response']['code'] == 200 ) return $result['body'];
		else return false;
	}
	/**
	 * @return API Request URI
	 **/
	abstract function build_request_url();
	/**
	 * @param string $data RAW API Response
	 * @return object Easier to manage data to save in the transient
	 **/
	abstract function prepare_data($data);
	/**
	 * Save transient data
	 * @param object $raw Raw API Response
	 * @return object Parsed, stripped down data, false on failure
	 **/
	private function set_transient($raw){
		$transient_data =& $this->prepare_data($raw);
		if ( $transient_data ) {
			if ( set_transient($this->transient_name, $transient_data, $this->transient_expire) )
				return $transient_data;
			else
				return false;
		} else {
			return false;
		}
	}
}
?>