curl.php

<?php

define( 'ACCESS_TOKEN',  'your-access-token-here' );
define( 'CLIENT_SECRET', 'your-client-secret-here' );
define( 'CONTENT_TYPE',  'application/json' );
define( 'ACCEPTS',       'application/json' );
define( 'ENDPOINT',      'https://api.fortnox.se/3/' );

function apiCall( $requestMethod, $entity, $body = null ){

  $curl = curl_init( ENDPOINT . $entity );
  $options = array(
    'Access-Token: '.  ACCESS_TOKEN  .'',
    'Client-Secret: '. CLIENT_SECRET .'',
    'Content-Type: '.  CONTENT_TYPE  .'',
    'Accept: '.        ACCEPTS       .''
  );

  curl_setopt( $curl, CURLOPT_RETURNTRANSFER, true );
  curl_setopt( $curl, CURLOPT_HTTPHEADER    , $options );
  curl_setopt( $curl, CURLOPT_CUSTOMREQUEST , $requestMethod );

  if( $requestMethod == 'POST' || $requestMethod == 'PUT' ){
    curl_setopt( $curl, CURLOPT_POSTFIELDS, $body );
  }

  $curlResponse = curl_exec( $curl );
    curl_close( $curl );
    return $curlResponse;
  }

?>