Revert "Fixing a compatibility problem with JsonSerializable interface for PHP versions prior to 5.4"

This reverts commit 986704a52465acc7a40f59740180f40fd0752f3f.
Revert "Fixing a compatibility problem with JsonSerializable interface for PHP versions prior to 5.4"

This reverts commit b7908de7a9f27d68e27e82a76b45760c49efb022.