Client for CrossRef REST API

1.0.0 2018-05-01 14:41 UTC

This package is auto-updated.

Last update: 2020-10-05 10:03:08 UTC


This is a library for the Crossref REST API written in PHP.

Crossref Metadata APIs logo PHP logo

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Table of contents


This is NOT an official library! The intent of this library is to provide an easy way to make requests to the CrossRef's REST API. You SHOULD read this documentation in conjunction with the official documentation.

Highlighted features:

Library's summary:

class RenanBr\CrossRefClient
    // Returns JSON decoded as array
    public function request($path, array $parameters = []);

    // Returns boolean
    public function exists($path);

    public function setUserAgent($userAgent);
    public function setCache(Psr\SimpleCache\CacheInterface $cache);
    public function setVersion($version);


composer require renanbr/crossref-client ^1



Singletons are single results. Retrieving metadata for a specific identifier (e.g. DOI, ISSN, funder_identifier) typically returns in a singleton result.


$client = new RenanBr\CrossRefClient();
$work = $client->request('works/10.1037/0003-066X.59.1.29');

The above example will output:

    [status] => ok
    [message-type] => work
    [message-version] => 1.0.0
    [message] => Array

            [DOI] => 10.1037/0003-066x.59.1.29
            [type] => journal-article


            [title] => Array
                    [0] => How the Mind Hurts and Heals the Body.


Determine existence of a singleton

(...) [You can] determine "existence" of a singleton. The advantage of this technique is that it is very fast because it does not return any metadata (...)


$client = new RenanBr\CrossRefClient();
$exists = $client->exists('members/98');

The above example will output:



Lists results can contain multiple entries. Searching or filtering typically returns a list result.

A list has two parts: Summary; and Items. Normally, an API list result will return both.


$client = new RenanBr\CrossRefClient();

$parameters = [
    'query' => 'global state',
    'filter' => [
        'has-orcid' => true,
$result = $client->request('works', $parameters);

foreach ($result['message']['items'] as $work) {
    // ...


Caching results

Cache data so you don't request the same data over and over again.


$client = new RenanBr\CrossRefClient();
$client->setCache(new voku\cache\CachePsr16());

// ...

The above example uses voku/simple-cache as cache implementation, but you can use any PSR-16 implementation because setCache() accept Psr\SimpleCache\CacheInterface as argument.

Identifying your script

As of September 18th 2017 any API queries that use HTTPS and have appropriate contact information will be directed to a special pool of API machines that are reserved for polite users.


$client = new RenanBr\CrossRefClient();
$client->setUserAgent('GroovyBib/1.1 (;');

// ...

The above example makes all subsequent requests attach the contact information given.

Tying to a specific major version

If you need to tie your implementation to a specific major version of the API, you can do so by using version-specific routes. The default route redirects to the most recent version of the API.


$client = new RenanBr\CrossRefClient();

// ...

The above example tie all subsequent requests to the API version v55.

Rate limits

By default, this library conforms to the rate limit imposed by the API for the current execution.

If you want to keep this behavior across multiple executions, you must configure the cache, as mentioned above.

Handling errors

As this library uses guzzlehttp/guzzle internally. Please refer to the Guzzle Exceptions documentation to see how to handle exceptions properly.