TwitterClient.php

<?php

namespace Drupal\my_module\Twitter;

use Symfony\Component\DependencyInjection\ContainerInterface;
use GuzzleHttp\Client;

class TwitterClient
{
    private $consumerKey;

    private $consumerSecret;

    private $bearerToken;

    private $client;

    public function __construct(Client $client, $consumerKey, $consumerSecret)
    {
        $this->client = $client;
        $this->consumerKey = $consumerKey;
        $this->consumerSecret = $consumerSecret; 
    }

    public function search($keywords, $length = 25)
    {
        $response = $this->client->request(
            'GET',
            sprintf('https://api.twitter.com/1.1/search/tweets.json?result_type=recent&count=%s&q=%s', $length, urlencode($keywords)),
            [
                'headers' => [
                    'Authorization' => 'Bearer ' . $this->getBearerToken()
                ]
            ]
        );

        if ($response->getStatusCode() != 200) {
            throw new \Exception('Twitter search failed with HTTP code ' . $response->getStatusCode());
        }

        return json_decode((string) $response->getBody(), true);
    }

    private function getBearerToken()
    {

        if ($this->bearerToken === null) {

            $response = $this->client->request('POST', 'https://api.twitter.com/oauth2/token', [
                'headers' => [
                    'Authorization' => 'Basic ' . $this->getBearerRequestToken(),
                    'Content-Type' => 'application/x-www-form-urlencoded;charset=UTF-8',
                ],
                'form_params' => [
                    'grant_type' => 'client_credentials'
                ]
            ]);

            if ($response->getStatusCode() != 200) {
                return null;
            }

            $body = (string) $response->getBody();
            $data = json_decode($body, true);
            $this->bearerToken = $data['access_token'];
        }

        return $this->bearerToken;
    }

    private function getBearerRequestToken()
    {
        $token = sprintf('%s:%s', urlencode($this->consumerKey), urlencode($this->consumerSecret));
        return base64_encode($token);
    }

    public static function createClient(ContainerInterface $container)
    {
        $econfig = $container->get('config.factory')->get('my_module.settings')->get('api');
        $client = $container->get('http_client');
        return new static($client, $config['consumer_key'], $config['consumer_secret']);
    }
}