These
functions
are
available
as
part
of
the
standard
module
,
which
is
always
available
.
There
is
no
installation
needed
to
use
these
functions
,
they
are
part
of
the
PHP
core
.
This
extension
does
not
define
any
configuration
directives
.
This
extension
does
not
define
any
resource
types
.
CASE_UPPER
and
CASE_LOWER
are
used
with
the
array_change_key_case(
)
CASE_UPPER
and
CASE_LOWER
are
used
with
the
array_change_key_case(
)
function
.
They
respectively
are
used
for
changing
a
string
to
upper
case
or
lower
case
.