$nochange = false
Use this to save a resource after retrieving. Since the
configuration variable is used in determining when to check the remote server, and
HTTP caching is used as well, it is possible for this scenario to arise:
retrieve REST resource
cache the resource
a few days later, retrieve the REST resource again
HTTP caching returns 304 not modified
In this situation, it doesn't make much sense to save the resource contents redundantly. Instead, the last access time can be saved in the cache id by passing true into the last parameter.
The REST resource's URL
Contents retrieved from the REST resource (ignored if the last parameter is true)
The ETag and LastModified headers retrieved from the remote server, used for HTTP caching.
If false, the cache is saved normally. If true, only the
parameter is saved in the cache id file, registering an HTTP cache hit.
throws no exceptions thrown
This function can not be called statically.