PHP namespaces for nested messages and enums (#4536)

* uses namespaces for nested messages and enums

* fixes namespaces for PHP dist

* fixes namespace for Descriptors, adds Cardinality and Kind

* fixes nested namespaces for reserved words and adds tests

* adds tests and generator fix for php class prefixes

* fixes escaping of protobuf packages, enum comments, misc others

* nice refactor of generated code

* adds class files for backwards compatibility

* simplifies code with templates

* adds compatibility files to makefile

* cleanup of generator and fixes nested namespace bug

* regenerates proto types

* remove internal BC classes

* adds deprecated warning, adds methods back

* simplifies if statement

* fixes dist files

* addresses review comments

* adds back TYPE_URL_PREFIX constant

* adds @deprecated to old nested class files

* skips tests which require a separate process when protobuf.so is enabled

* Adds tests for legacy nested classes that do not require separate processes to test

* uses legacy names for GPBUtil message check

* adds block for IDE @deprecated message

* Namespace for nested message/enum in c extension

* Remove unused code

1 files changed, 17 insertions, 0 deletions

diff --git a/php/tests/proto/empty/echo.proto b/php/tests/proto/empty/echo.proto
new file mode 100644
index 00000000..1817018d
--- /dev/null
+++ b/php/tests/proto/empty/echo.proto
@@ -0,0 +1,17 @@
+syntax = "proto3";
+
+package empty.echo;
+
+message TestEmptyPackage {
+  int32 a = 1;
+
+  // Test nested messages, enums, and reserved names
+  NestedMessage nested_message = 2;
+  NestedEnum nested_enum = 3;
+  message NestedMessage {
+    int32 a = 1;
+  }
+  enum NestedEnum {
+      ZERO = 0;
+  };
+}