This SDK now requires PHP 7.0, which means all files now use the strict_types directive and scalar type declarations whenever possible.
The class Contentful\Core\Api\BaseClient no longer requires the method getSdkVersion to be defined, but it now requires getPackageName, which should return the Packagist name (e.g. contentful/core). This name will then be used to automatically infer the SDK version number. This method, along with getVersion, getSdkName, and getApiContentType, is defined as static.
Abstract class BaseClients now implements Contentful\Core\Api\ClientInterface, which means classes extending this must implement the request method. In the BaseClient the previous request method has been renamed callApi, and the baseUri option has been renamed host.
The class Contentful\Core\Log\Timer was deprecated in version 1.1 and has now been removed.
The method Contentful\Core\Api\BaseQuery::where() no longer accepts a third parameter. Now simply include that as part of the first parameter:
// Before
$query->where('sys.id', $someId, 'ne');
// After
$query->where('sys.id[ne]', $someId);