The Slice compilers can optionally generate checksums of Slice definitions. For
--checksum option causes the compiler to generate checksums. The checksums are installed automatically when the PHP code is first parsed; no action is required by the application.
In order to verify a server's checksums, a client could simply compare the two array objects using a comparison operator. However, this is not feasible if it is possible that the server might return a superset of the client's checksums. A more general solution is to iterate over the local checksums as demonstrated below:
In this example, the client first verifies that the server's dictionary contains an entry for each Slice type ID, and then it proceeds to compare the checksums.