mb_convert_case() returns case
folded version of string
converted in the way specified by
mode.
mode can be one of
MB_CASE_UPPER, MB_CASE_LOWER or MB_CASE_TITLE.
encoding specifies the
encoding of str; if
omitted, the internal character encoding value will be
used.
The return value is str with the appropriate case
folding applied.
By contrast to the standard case folding functions such
as
strtolower() and
strtoupper(), case folding is
performed on the basis of the Unicode character properties.
Thus the behaviour of this function is not affected by locale
settings and it can convert any characters that have
'alphabetic' property, such as A-umlaut (ĩ.
For more information about the Unicode properties,
please see
http://www.unicode.org/unicode/reports/tr21/.
See also mb_strtolower(),
mb_strtoupper(),
strtolower(),
strtoupper().