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, 30 insertions, 0 deletions

diff --git a/php/src/Google/Protobuf/Internal/FieldDescriptorProto/Label.php b/php/src/Google/Protobuf/Internal/FieldDescriptorProto/Label.php
new file mode 100644
index 00000000..b105088e
--- /dev/null
+++ b/php/src/Google/Protobuf/Internal/FieldDescriptorProto/Label.php
@@ -0,0 +1,30 @@
+<?php
+# Generated by the protocol buffer compiler.  DO NOT EDIT!
+# source: google/protobuf/descriptor.proto
+
+namespace Google\Protobuf\Internal\FieldDescriptorProto;
+
+/**
+ * Protobuf type <code>google.protobuf.FieldDescriptorProto.Label</code>
+ */
+class Label
+{
+    /**
+     * 0 is reserved for errors
+     *
+     * Generated from protobuf enum <code>LABEL_OPTIONAL = 1;</code>
+     */
+    const LABEL_OPTIONAL = 1;
+    /**
+     * Generated from protobuf enum <code>LABEL_REQUIRED = 2;</code>
+     */
+    const LABEL_REQUIRED = 2;
+    /**
+     * Generated from protobuf enum <code>LABEL_REPEATED = 3;</code>
+     */
+    const LABEL_REPEATED = 3;
+}
+
+// Adding a class alias for backwards compatibility with the previous class name.
+class_alias(Label::class, \Google\Protobuf\Internal\FieldDescriptorProto_Label::class);
+