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Restful Service

RestfulService is used to enable connections to remote web services through PHP's curl command. It provides an interface and utility functions for generating a valid request and parsing the response returned from the web service.

RestfulService currently only supports XML. It has no JSON support at this stage.

Examples

Creating a new RestfulObject

getWellingtonWeather queries the Yahoo Weather API for an XML file of the latest weather information. We pass a query string parameter q with the search query and then convert the resulting XML data to an ArrayList object to display in the template.

mysite/code/Page.php

public function getWellingtonWeather() {
    $fetch = new RestfulService(
        'https://query.yahooapis.com/v1/public/yql'
    );

    $fetch->setQueryString(array(
        'q' => 'select * from weather.forecast where woeid in (select woeid from geo.places(1) where text="Wellington, NZ")'
    ));

    // perform the query
    $conn = $fetch->request();

    // parse the XML body
    $msgs = $fetch->getValues($conn->getBody(), "results");

    // generate an object our templates can read
    $output = new ArrayList();

    if($msgs) {
        foreach($msgs as $msg) {
            $output->push(new ArrayData(array(
                'Description' => Convert::xml2raw($msg->channel_item_description)
            )));
        }
    }

    return $output;
}

Features

Basic Authenication

$service = new RestfulService("http://example.harvestapp.com");
$service->basicAuth('username', 'password');

Make multiple requests

$service = new RestfulService("http://example.harvestapp.com");

$peopleXML = $service->request('/people');
$people = $service->getValues($peopleXML, 'user');

// ...

$taskXML = $service->request('/tasks');
$tasks = $service->getValues($taskXML, 'task');

Caching

To set the cache interval you can pass it as the 2nd argument to constructor.

$expiry = 60 * 60; // 1 hour;

$request = new RestfulService("http://example.harvestapp.com", $expiry );

Getting Values & Attributes

You can traverse through document tree to get the values or attribute of a particular node using XPath. Take for example the following XML that is returned.

<entries>
     <entry id='12'>Sally</entry>
     <entry id='15'>Ted</entry>
     <entry id='30'>Matt</entry>
     <entry id='22'>John</entry>
</entries>

To extract the id attributes of the entries use:

$this->getAttributes($xml, "entries", "entry");

// array(array('id' => 12), array('id' => '15'), ..)

To extract the values (the names) of the entries use:

$this->getValues($xml, "entries", "entry");

// array('Sally', 'Ted', 'Matt', 'John')

Searching for Values & Attributes

If you don't know the exact position of DOM tree where the node will appear you can use xpath to search for the node.

This is the recommended method for retrieving values of name spaced nodes.
<media:guide>
     <media:entry id="2030">video</media:entry>
</media:guide>

To get the value of entry node with the namespace media, use:

$this->searchValue($response, "//media:guide/media:entry");

// array('video');

Best Practices

Handling Errors

If the web service returned an error (for example, API key not available or inadequate parameters), RestfulService can delegate the error handling to it's descendant class. To handle the errors, subclass `RestfulService and define a function called errorCatch.

<?php

class MyRestfulService extends RestfulService {

    public function errorCatch($response) {
        $err_msg = $response;

        if(strpos($err_msg, '<') === false) {
            user_error("YouTube Service Error : $err_msg", E_USER_ERROR);
        }

        return $response;
    }
}

If you want to bypass error handling, define checkErrors in the constructor for RestfulService

<?php

class MyRestfulService extends RestfulService {

    public function __construct($expiry = NULL) {
        parent::__construct('http://www.flickr.com/services/rest/', $expiry);

        $this->checkErrors = false;
    }
}

How to's

API Documentation