Letter Casing in PHP

Letter casing functions are available in the core language and have Unicode semantics.

$lowercase = mb_convert_case($str, MB_CASE_UPPER, 'UTF-8');
$uppercase = mb_convert_case($str, MB_CASE_LOWER, 'UTF-8');
$titlecase = mb_convert_case($str, MB_CASE_TITLE, 'UTF-8');
# case folding?

The mb_convert_case function was added in PHP 4.3.