Function: Returns a comma-separated string or array of functions that have been called to get to the current point in code.

Function: Retrieves IDs that are not already present in the cache.

Function: Tests if the current device has the capability to upload files.

Function: Tests if a given path is a stream URL

Function: Returns true.

Function: Returns false.

Function: Returns 0.

Function: Returns an empty array.

Function: Returns null.

Function: Returns an empty string.