A Zend Framework class to fetch EC2 instance meta-data

Metadata.php

<?php
require_once 'Zend/Service/Abstract.php';
/**
 * 
 * 
 * @author zircote@zircote.com
 * 
 * <code>
 * <?php
 * $metadata = new Zircote_Service_Ec2_Metadata;
 * echo $metadata->amiID;
 * echo $metadata->hostname;
 * echo $metadata->instanceId
 * echo $metadata->kernelId
 * echo $metadata->userData;
 * echo $metadata->publicHostname;
 * </code>
 * <p>CLI example (but note curl -s would probably be more suitable)</p>
 * <code>
 * #!/usr/bin/env php
 * <?php
 * require_once 'Zircote/Service/Ec2/Metadata.php';
 * $metadata = new Zircote_Service_Ec2_Metadata;
 * try{
 *     file_put_contents('php://stdout',$metadata->__get($_SERVER['argv'][1]));
 * } catch (Exception $e){
 *     file_put_contents('php://stderr', $e->getMessage());
 *     exit(0);
 * }
 * </code>
 */
class Zircote_Service_Ec2_Metadata extends Zend_Service_Abstract
{
    protected $_endpoint = 'http://169.254.169.254';
    protected $_methods = array(
        'amiID' => '/latest/meta-data/ami-id',
        'amiLaunchIndex' => '/latest/meta-data/ami-launch-index',
        'amiManifestPath' => '/latest/meta-data/ami-manifest-path',
        'ancestorAmiIds' => '/latest/meta-data/ancestor-ami-ids',
        'blockDeviceMapping' => '/latest/meta-data/block-device-mapping/',
        'hostname' => '/latest/meta-data/hostname',
        'instanceAction' => '/latest/meta-data/instance-action',
        'instanceId' => '/latest/meta-data/instance-id',
        'instanceType' => '/latest/meta-data/instance-type',
        'kernelId' => '/latest/meta-data/kernel-id',
        'localHostname' => '/latest/meta-data/local-hostname',
        'localIpv4' => '/latest/meta-data/local-ipv4',
        'placement' => '/latest/meta-data/placement/',
        'publicHostname' => '/latest/meta-data/public-hostname',
        'publicIpv4' => '/latest/meta-data/public-ipv4',
        'publicKeys' => '/latest/meta-data/public-keys/',
        'ramdiskId' => '/latest/meta-data/ramdisk-id',
        'reservationId' => '/latest/meta-data/reservation-id',
        'securityGroups' => '/latest/meta-data/security-groups',
        'userData' => '/latest/user-data',
    );

    public function __get($name)
    {
        if(!array_key_exists($name, $this->_methods)){
            throw new Exception(sprintf('method [%s] does not exist', $name));
        }
        self::getHttpClient()->setUri($this->_endpoint)
            ->getUri()->setPath($this->_methods[$name]);
        $result = self::getHttpClient()->request();
        if($result->getStatus() == 200){
            return $result->getBody();
        } else {
            return false;
        }
    }
}