Fix Any json encoding/decoding in php (#5496)

* Fix Any json encoding/decoding in php

* Fix comments

php/tests/gdb_test.sh

diff --git a/php/tests/gdb_test.sh b/php/tests/gdb_test.sh
index 36fa31b..da5f3f3 100755
--- a/php/tests/gdb_test.sh
+++ b/php/tests/gdb_test.sh
@@ -11,7 +11,8 @@
 # gdb --args php -dextension=../ext/google/protobuf/modules/protobuf.so `which
 # phpunit` --bootstrap autoload.php tmp_test.php
 #
-gdb --args php -dextension=../ext/google/protobuf/modules/protobuf.so `which phpunit` --bootstrap autoload.php generated_class_test.php
+# gdb --args php -dextension=../ext/google/protobuf/modules/protobuf.so `which phpunit` --bootstrap autoload.php generated_class_test.php
+gdb --args php -dextension=../ext/google/protobuf/modules/protobuf.so `which phpunit` --bootstrap autoload.php encode_decode_test.php
 #
 # gdb --args php -dextension=../ext/google/protobuf/modules/protobuf.so memory_leak_test.php
 #