* Support grpc-status-details-bin for ApiException::getErrorDetails ([#614](https://github.com/googleapis/gax-php/issues/614)) ([c44ad0c](https://github.com/googleapis/gax-php/commit/c44ad0c068586b635a3f6b325e157c116f68065e))
* Add ApiException::getErrorDetails() for retrieval of additional exception info ([#611](https://github.com/googleapis/gax-php/issues/611)) ([be7402a](https://github.com/googleapis/gax-php/commit/be7402a94d1c4201e1ca03cdd3bab6c01adb0c24))
* Use self:: instead of $this-> for static validation methods in GapicClientTrait validation ([#643](https://github.com/googleapis/gax-php/issues/643)) ([5ba2b20](https://github.com/googleapis/gax-php/commit/5ba2b200c16b78b10e3dddf5ac6a2c5cd7eb8641))
* Add return type to `offsetGet` ([#633](https://github.com/googleapis/gax-php/issues/633)) ([b77c12d](https://github.com/googleapis/gax-php/commit/b77c12dc959e8434fcd1f7f08cedaa84cdfb00a4))
* Add the rpcName to the BIDI stream opening request ([#630](https://github.com/googleapis/gax-php/issues/630)) ([9c61d8f](https://github.com/googleapis/gax-php/commit/9c61d8f2bd09731d5f22c22eb81895eaf4db2031))
* Make options classes fluid ([#618](https://github.com/googleapis/gax-php/issues/618)) ([427b46e](https://github.com/googleapis/gax-php/commit/427b46e91b3881fd0da361b5b351c6dda47e640a))
### Bug Fixes
* Update protobuf RepeatedField to new namespace ([#624](https://github.com/googleapis/gax-php/issues/624)) ([3558cc4](https://github.com/googleapis/gax-php/commit/3558cc49139861fa411c77b33f457467ec8daa97))
* Support client options in ClientOptionsTrait::buildClientOptions ([#621](https://github.com/googleapis/gax-php/issues/621)) ([68e2336](https://github.com/googleapis/gax-php/commit/68e23369657b1740fffe480f96d9d7b04e3e38c2))
### Bug Fixes
* Ensure compute request build parameters have the operation ID last ([#625](https://github.com/googleapis/gax-php/issues/625)) ([f90ab28](https://github.com/googleapis/gax-php/commit/f90ab28cea6bbbd00f2a652a6d77babb69b2ada8))
* Add logging to the supported transports ([#585](https://github.com/googleapis/gax-php/issues/585)) ([819a677](https://github.com/googleapis/gax-php/commit/819a677e0d89d75662b30a1dbdd45f6a610d9f0c))
* Add `InsecureRequestBuilder` for emulator ([#582](https://github.com/googleapis/gax-php/issues/582)) ([cc1d047](https://github.com/googleapis/gax-php/commit/cc1d0472a1caf31bb3ecd98da1d6b8588f95b63a))
* **docs:** Use doctum shared workflow for reference docs ([#578](https://github.com/googleapis/gax-php/issues/578)) ([021763f](https://github.com/googleapis/gax-php/commit/021763f255acaffda6ebe34a9d1a01c2bd187326))
* Support for API Key client option ([#351](https://github.com/googleapis/gax-php/issues/351)) ([ab7f04f](https://github.com/googleapis/gax-php/commit/ab7f04fd8c9f7ed33a58155ae6b9e740f365ac2a))
### Bug Fixes
* **tests:** Skip docs tests from forks ([#591](https://github.com/googleapis/gax-php/issues/591)) ([35ae9f7](https://github.com/googleapis/gax-php/commit/35ae9f708d3ef937308d266e3a012296ce8606fc))
* Support new surface operations clients ([#569](https://github.com/googleapis/gax-php/issues/569)) ([fa06e73](https://github.com/googleapis/gax-php/commit/fa06e738fc63a3b9f70a26e6d20f30c582ef1870))
* Support V2 OperationsClient in OperationResponse ([#564](https://github.com/googleapis/gax-php/issues/564)) ([7f8bb13](https://github.com/googleapis/gax-php/commit/7f8bb13f78463b1e7f2289ce5514763992806e5e))
* Add a custom encoder in Serializer ([#554](https://github.com/googleapis/gax-php/issues/554)) ([be28b5a](https://github.com/googleapis/gax-php/commit/be28b5a859b674a3d398bdaab7ed86b93dd7a593))
* Add the api header to the GapicClientTrait ([#553](https://github.com/googleapis/gax-php/issues/553)) ([cc102eb](https://github.com/googleapis/gax-php/commit/cc102ebdfd63019b1e6bcd51515be2a2cb13534d))
### Bug Fixes
* Add caching and micro optimizations in Serializer ([5a5d8a7](https://github.com/googleapis/gax-php/commit/5a5d8a763d8e2d470a6d960b788e7d2a938cd64f))
* Auto Populate fields configured for auto population in Rpc Request Message ([#543](https://github.com/googleapis/gax-php/issues/543)) ([99d6b89](https://github.com/googleapis/gax-php/commit/99d6b899ddf55d51fab976844c1e0f8fe9918a52))
* Make the default authHttpHandler in CredentialsWrapper null ([#544](https://github.com/googleapis/gax-php/issues/544)) ([2a25eea](https://github.com/googleapis/gax-php/commit/2a25eeacadf2f783f64b4eca4f94e067ddef3eaa))
* Universe domain check for grpc transport ([#534](https://github.com/googleapis/gax-php/issues/534)) ([1026d8a](https://github.com/googleapis/gax-php/commit/1026d8aec73e0aad8949a86ee7575e3edb3d56be))
* Typo in TransportOptions option name ([#530](https://github.com/googleapis/gax-php/issues/530)) ([6914fe0](https://github.com/googleapis/gax-php/commit/6914fe04554867bd827be6596fafc751a3d7621a))
* Implement ProjectIdProviderInterface in CredentialsWrapper ([#523](https://github.com/googleapis/gax-php/issues/523)) ([b56a463](https://github.com/googleapis/gax-php/commit/b56a4635abfeeec08895202da8218e9ba915413e))
* Update ArrayTrait to be consistent with Core ([#526](https://github.com/googleapis/gax-php/issues/526)) ([8e44185](https://github.com/googleapis/gax-php/commit/8e44185dd6f8f8f9ef5b136776cba61ec7a8b8f6))
### Bug Fixes
* Correct exception type for Guzzle promise ([#521](https://github.com/googleapis/gax-php/issues/521)) ([7129373](https://github.com/googleapis/gax-php/commit/712937339c134e1d92cab5fa736cfe1bbcd7f343))
* CallOptions should use transportOptions ([#513](https://github.com/googleapis/gax-php/issues/513)) ([2d45ee1](https://github.com/googleapis/gax-php/commit/2d45ee187cdc3619b30c51b653b508718baf3af4))
* Ensure modifyClientOptions is called for new surface clients ([#515](https://github.com/googleapis/gax-php/issues/515)) ([68231b8](https://github.com/googleapis/gax-php/commit/68231b896dec8efb86f8986aefba3d247d2a2d1c))
* Add support for universe domain ([#502](https://github.com/googleapis/gax-php/issues/502)) ([5a26fac](https://github.com/googleapis/gax-php/commit/5a26facad5c2e5c30945987c422bb78a3fffb9b1))
* Interface and methods for middleware stack ([#473](https://github.com/googleapis/gax-php/issues/473)) ([766da7b](https://github.com/googleapis/gax-php/commit/766da7b369409ec1b29376b533e7f22ee7f745f4))
### Bug Fixes
* Accept throwable for retry settings ([#509](https://github.com/googleapis/gax-php/issues/509)) ([5af9c3c](https://github.com/googleapis/gax-php/commit/5af9c3c650419c8f1a590783e954cd11dc1f0d56))
* Ensure NewClientSurface works for consoldiated v2 clients ([#493](https://github.com/googleapis/gax-php/issues/493)) ([cb8706e](https://github.com/googleapis/gax-php/commit/cb8706ef9211a1e43f733d2c8f272a330c2fa792))
* Typesafety for new surface client options ([#450](https://github.com/googleapis/gax-php/issues/450)) ([21550c5](https://github.com/googleapis/gax-php/commit/21550c5bf07f178f2043b0630f3ac34fcc3a05e0))
* Sets api headers for "gcloud-php-new" and "gcloud-php-legacy" surface versions ([#470](https://github.com/googleapis/gax-php/issues/470)) ([2d8ccff](https://github.com/googleapis/gax-php/commit/2d8ccff419a076ee2fe9d3dc7ecd5509c74afb4c))
* Ensure timeout set by RetryMiddleware is int not float ([#462](https://github.com/googleapis/gax-php/issues/462)) ([9d4c7fa](https://github.com/googleapis/gax-php/commit/9d4c7fa89445c63ec0bf4745ed9d98fd185ef51f))
* Default value for error message in createFromRequestException ([#463](https://github.com/googleapis/gax-php/issues/463)) ([7552d22](https://github.com/googleapis/gax-php/commit/7552d22241c2f488606e9546efdd6edea356ee9a))
* Ensure cache is used in calls to ADC::onGCE ([#441](https://github.com/googleapis/gax-php/issues/441)) ([64a4184](https://github.com/googleapis/gax-php/commit/64a4184ab69d13104d269b15a55d4b8b2515b5a6))
* Ensure metadata return type is loaded into descriptor pool ([#439](https://github.com/googleapis/gax-php/issues/439)) ([a40cf8d](https://github.com/googleapis/gax-php/commit/a40cf8d87ac9aa45d18239456e2e4c96653f1a6c))
* Implicit conversion from float to int warning ([#438](https://github.com/googleapis/gax-php/issues/438)) ([1cb62ad](https://github.com/googleapis/gax-php/commit/1cb62ad3d92ace0518017abc972e912b339f1b56))
* use interfaceOverride instead of param ([#419](https://github.com/googleapis/gax-php/issues/419)) ([9dd5bc9](https://github.com/googleapis/gax-php/commit/9dd5bc91c4becfd2a0832288ab2406c3d224618e))
* use responseType for custom operations ([#413](https://github.com/googleapis/gax-php/issues/413)) ([b643adf](https://github.com/googleapis/gax-php/commit/b643adfc44dd9fe82b0919e5b34edd00c7cdbb1f))
* drop support for PHP 5.6 ([#397](https://github.com/googleapis/gax-php/issues/397)) ([b888b24](https://github.com/googleapis/gax-php/commit/b888b24e0e223784e22dbbbe27fe0284cdcdfc35))
* move LongRunning classes to a standalone package ([#401](https://github.com/googleapis/gax-php/issues/401)) ([1747125](https://github.com/googleapis/gax-php/commit/1747125c84dcc6d42390de7e78d2e326884e1073))