Use dlvr.it shortlinks in WordPress

api.php

<?php
// http://pmg.co
class wpDlvrit
{
	protected $key;

	function __construct( $key = false )
	{
		$this->set_key( $key );
	}

	function set_key( $key )
	{
		if( $key )
		{
			$this->key = $key;
		}
		else
		{
			$opts = get_option( 'wpdlvrit_options' );
			$key = isset( $opts['api_key'] ) ? $opts['api_key'] : new WP_Error();
			if( is_wp_error( $key ) )
			{
				$key->add( 'no_api_key', __( "You haven't set up your Dlvr.it API key yet!" ) );
			}
			$this->key = $key;
		}
	}

	function get_key()
	{
		return $this->key;
	}

	function get_routes( $format = 'json' )
	{
		$data = array(
			'method' => 'POST',
			'body'   => array( 'key' => $this->get_key() )
		);
		$url = 'http://api.dlvr.it/1/routes.' . $format;
		$response = wp_remote_post( $url, $data );

		$response = $this->validate( $response );

		return $response;
	}

	function get_accounts( $format = 'json' )
	{
		$data = array(
			'method' => 'POST',
			'body'   => array( 'key' => $this->get_key() )
		);
		$url = 'http://api.dlvr.it/1/accounts.' . $format;
		$response = wp_remote_post( $url, $data );

		$response = $this->validate( $response );

		return $response;
	}

	function get_shortlink( $long_url, $format = 'json' )
	{
		$data = array(
			'method' => 'POST',
			'body'   => array( 
							'key' => $this->get_key(),
							'url' => $long_url
						)
		);

		$url = 'http://api.dlvr.it/1/shorten.' . $format;

		$response = wp_remote_post( $url, $data );

		$response = $this->validate( $response );
		
		return $response;
	}

	function post_to_account( $account_id, $message, $format = 'json' )
	{
		$data = array(
			'method' => 'POST',
			'body'   => array( 
							'key' => $this->get_key(),
							'id'  => $account_id,
							'msg' => $message
						)
		);

		$url = 'http://api.dlvr.it/1/postToAccount.' . $format;

		$response = wp_remote_post( $url, $data );

		$response = $this->validate( $response );

		return $response;
	}

	function post_to_route( $account_id, $message, $format = 'json' )
	{
		$data = array(
			'method' => 'POST',
			'body'   => array( 
							'key' => $this->get_key(),
							'id'  => $account_id,
							'msg' => $message
						)
		);

		$url = 'http://api.dlvr.it/1/postToRoute.' . $format;

		$response = wp_remote_post( $url, $data );

		$response = $this->validate( $response );
		
	}

	// Validate our responses ...
	protected function validate( $response )
	{
		if( is_wp_error( $response ) || 200 != $response['response']['code'] ) return false;

		return $response;
	}
}

dlvrit-shortlinks.php

<?php
/*
Plugin Name: WP Dlvr.it Shortlinks
Plugin URI: http://pmg.co/
Description: Uses Dlvr.it as WordPress's custom shortlink service
Version: n/a
Author: Christopher Davis
Author URI: http://pmg.co/people/chris
*/

// call in our dlvir API.
require_once( plugin_dir_path( __FILE__ ) . 'api.php' );

add_filter( 'get_shortlink', 'pmgtut2_get_shortlink', 10, 3 );
function pmgtut2_get_shortlink( $link, $id, $context )
{
	if( 'query' == $context && is_singular() )
	{
		$id = get_queried_object_id();
	} 
	
	if( $dlvrit = get_post_meta( $id, '_pmg_dlvrit_url', true ) )
	{
		return $dlvrit;
	}
	else
	{
		$dlvrit = new wpDlvrit( 'your_api_id' );
		$long = esc_url( get_permalink( $id ) );
		$short = $dlvrit->get_shortlink( $long );
		
		// If there's a problem, return the original link
		if( ! $short ) return $link;
		
		$body = json_decode( $short['body'] );
		
		// uh oh, return original link
		if( ! isset( $body[0]->short ) ) return $link;
		
		update_post_meta( $id, '_pmg_dlvrit_url', esc_url( $body[0]->short ) );
		return esc_url( $body[0]->short );
	}
}