SYNOPSIS
        object * filter_objects(object *arr, string fun, mixed extra, ...)

DESCRIPTION
        Similar to filter_array() but calls arr[n]->fun(extra, ...).
        If the call returns != 0, the object arr[n] ist included in
        the returned array.
        0-entries in arr are ignored.

SEE ALSO
        filter(E), map(E), map_objects(E)