There are quite a few functions in PHP which you can call with more
than one name. In some cases there is no preferred name among the
multiple ones, is_int() and
is_integer() are equally good for example.
However there are functions which changed names because of an API
cleanup or some other reason and the old names are only kept as
aliases for backward compatibility. It is usually a bad idea to use
these kind of aliases, as they may be bound to obsolescence or
renaming, which will lead to unportable script. This list is provided
to help those who want to upgrade their old scripts to newer syntax.