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, 6 insertions, 29 deletions

diff --git a/php/src/Google/Protobuf/Field_Cardinality.php b/php/src/Google/Protobuf/Field_Cardinality.php
index 422587ca..dff8f893 100644
--- a/php/src/Google/Protobuf/Field_Cardinality.php
+++ b/php/src/Google/Protobuf/Field_Cardinality.php
@@ -4,36 +4,13 @@
 
 namespace Google\Protobuf;
 
-/**
- * Whether a field is optional, required, or repeated.
- *
- * Protobuf enum <code>Google\Protobuf\Field\Cardinality</code>
- */
-class Field_Cardinality
-{
+if (false) {
     /**
-     * For fields with unknown cardinality.
-     *
-     * Generated from protobuf enum <code>CARDINALITY_UNKNOWN = 0;</code>
+     * This class is deprecated. Use Google\Protobuf\Field\Cardinality instead.
+     * @deprecated
      */
-    const CARDINALITY_UNKNOWN = 0;
-    /**
-     * For optional fields.
-     *
-     * Generated from protobuf enum <code>CARDINALITY_OPTIONAL = 1;</code>
-     */
-    const CARDINALITY_OPTIONAL = 1;
-    /**
-     * For required fields. Proto2 syntax only.
-     *
-     * Generated from protobuf enum <code>CARDINALITY_REQUIRED = 2;</code>
-     */
-    const CARDINALITY_REQUIRED = 2;
-    /**
-     * For repeated fields.
-     *
-     * Generated from protobuf enum <code>CARDINALITY_REPEATED = 3;</code>
-     */
-    const CARDINALITY_REPEATED = 3;
+    class Field_Cardinality {}
 }
+class_exists(Field\Cardinality::class);
+@trigger_error('Google\Protobuf\Field_Cardinality is deprecated and will be removed in the next major release. Use Google\Protobuf\Field\Cardinality instead', E_USER_DEPRECATED);