function idxv($map, $path, $default)

libphutil Technical Documentation (Core Utilities)

Access a sequence of array indexes, retrieving a deeply nested value if it exists or a default if it does not.

For example, idxv($dict, array('a', 'b', 'c')) accesses the key at $dict['a']['b']['c'], if it exists. If it does not, or any intermediate value is not itself an array, it returns the defualt value.