sample-request.php

<?php 

function adding_products() {
	// API call  
	$feed = new Boats_API_Client( 'yachtall', 'en', array( 'code' => 'xxx', 'site_id' => 'xxx', 'bt_vers' => '3.0', 'api_vers' => '1.0' ) );

	echo '<pre>';
		var_dump($feed);   
	echo '</pre>'; 

} 

wordpress-api-client.php

<?php

/**
 * WordPress JSON API client.
 *  
 * @author Joseph VanTine 
 * @link https://dealersleague.com 
 */
class Boats_API_Client {

    /**
     * Base path for all API user resources.
     *
     * @var string
     */

    const YACHTALL_LIST = 'https://api.yachtall.com/en/boat-data';

    /**
     * Base URL for the WordPress site that the client is connecting to.
     *
     * @var string
     */
    private $feed_name;  

    /**
     * Language
     *
     * @var string
     */
    private $lang;

    /**
     * API args
     *
     * @var string
     */
    private $args; 

    /**
     * Constructor.
     *
     * @param string  $feed_name
     * @param string  $lang
     * @param string  $args 
     */
    public function __construct( $feed_name, $lang, $args = array() ) { 
        $this->feed_name = $feed_name; 
        $this->lang      = $lang;
        $this->args      = $args; 
    }

    /**
     * Retrieve all of the boats.
     *
     * @param  array   $feed_name
     * @param  string  $args  
     *
     * @return array|WP_Error
     */
    public function get_feed( $args = array() ) { 

        return $this->get( $this->build_url( $args ) );
    } 

    /**
     * Builds a full API request URL from the given endpoint URL and query string arguments.
     *
     * @param string $endpoint
     * @param array  $query
     *
     * @return string
     */
    private function build_url( $args ) {

        if ( $args['is_single'] == 'false' ) {
            $is_single = '/boats/';
        } else {
            $is_single = '/boat/';
        }
        
        if ( $this->feed_name == 'yachtall' ) {
            $url = self::YACHTALL_LIST.$is_single;  
        }

        if ( !empty( $this->args ) ) {
            $url .= '?'.rawurldecode(http_build_query( $this->args ));
        }

        if ( $args['is_single'] == 'true' && !empty( $args['id'] ) ) {
            $url .= '&bid='.$args['id'];
        } 
            
        return $url;
    }


    /**
     * Converts the given response to a WP_Error object.
     *
     * @param array $response
     *
     * @return WP_Error
     */
    private function convert_response_to_error(array $response)
    {
        $response = $this->decode_response($response);
        $error    = new WP_Error();

        if ($response instanceof WP_Error) {
            $error = $response;
        } elseif (is_array($response)) {
            array_walk($response, array($this, 'add_response_error'), $error);
        }

        return $error;          
    }

    /**
     * Decodes the JSON object returned in given response. Returns a WP_Error on error.
     *
     * @param array $response
     *
     * @return array|WP_Error
     */
    private function decode_response(array $response)
    {
        $decoded = array();
        $headers = $this->get_response_headers($response); 

        if (!isset($headers['content-type']) || false === stripos($headers['content-type'], 'application/json')) {
            return new WP_Error('invalid_response', 'The content-type of the response needs to be "application/json".');
        }

        if (isset($response['body'])) {
            $decoded = json_decode($response['body'], true);
        }

        if (null === $decoded) {
            return new WP_Error('invalid_json', 'The JSON response couldn\'t be decoded.');
        }

        return $decoded;
    }

    /**
     * Performs a GET request using the WordPress HTTP transport. Returns a WP_Error
     * on error.
     *
     * @param string $url
     * @param array  $args
     *
     * @return array|WP_Error
     */
    private function get( $response ) {

        $response = wp_remote_request( $response ); 

        if ( is_array( $response ) && $this->is_successful($response) ) {
            $response = $this->decode_response($response); 
        } elseif ( !is_array( $response ) && !$this->is_successful($response) ) {
            $response = $this->convert_response_to_error($response); 
        }

        return $response;
    }

    /**
     * Extracts the response headers from the given response.
     *
     * @param array $response
     *
     * @return array
     */
    private function get_response_headers(array $response)
    {
        if (!isset($response['headers']) || !is_array($response['headers'])) {
            $response = $response['headers'];
        }

        return $response;
    }

    /**
     * Extracts the status code from the given response.
     *
     * @param array $response
     *
     * @return int|null
     */
    private function get_response_status_code(array $response)
    {
        if (!isset($response['response']) || !isset($response['response']['code'])) {
            return null;
        }

        return $response['response']['code'];
    }

    /**
     * Checks if the given response is considered successful as per the HTTP specification.
     * This means that the response has a 2xx status code.
     *
     * @param array $response
     *
     * @return bool
     */
    private function is_successful(array $response)
    {
        $status_code = $this->get_response_status_code($response);

        if (null === $status_code) {
            return false;
        }

        return $status_code >= 200 && $status_code < 300;
    }
}