## Important behavior changes in this release
If you use the OpenTracing API, the OpenTracing compatible tracer will no longer be returned from `OpenTracing\GlobalTracer::get` automatically. See #899 or [the documentation](https://docs.datadoghq.com/tracing/opentracing/php/) for more details.

On PHP 7, `dd_trace` will no longer work on internal functions e.g. `curl_exec`; use `dd_trace_method` or `dd_trace_function` instead. Additionally, when targeting internal functions they also need to be added to the environment variable `DD_TRACE_TRACED_INTERNAL_FUNCTIONS` which is a comma separated list e.g. `DD_TRACE_TRACED_INTERNAL_FUNCTIONS=array_sum,mt_rand,DateTime::add`. These two changes enable a significant performance optimization.

### Changed
- Avoid usage of spl_autoload_register while still allowing noop manual instrumentation without ext installed #877
- Sandbox Slim integration #878
- Sandbox Lumen integration #884
- Sandbox CakePHP integration #898
- Remove legacy hook for OpenTracing #899
- Noop the legacy API when a potentially conflicting module detected #900, #905
- Move the request init hook to `auto_prepend_file` #907
- Optimize internal functions handlers at startup (PHP 7) #895

### Fixed
- Fix early return in dd-doctor #894 (thank @tatsuo48!)
- Fix opcache check in dd-doctor #896 - thanks @tatsuo48
- Update CONTRIBUTING.md #897 - thanks @askkaz