Below is a description of what steps should be performed in order to get russian characters show. Please substitute appropriate values for the other languages.

CASE #1 Mandrake 9.1, KDE 3.1

1.
edit file /etc/profile
add at the end of file:
export LANG=ru_RU.KOI8-R
export LC_ALL=ru_RU.KOI8-R

then Reboot Linux

2.
Configuration -> Other -> LocalDrake
set Russian

3.
Configuration -> Control Center -> Accessibility -> Country - Region & Language
add Russian language. Make sure that English language is listed there also as you probably want to type latin characters too, not only Russian ones.

4.
Configuration -> Control Center -> Accessibility -> Keyboard Layout
Enable keyboard layout
set Additional layout "Russian"
(check that U.S.English is there too)

5.
PhpEd -> Settings -> Editor
set Character set to KOI8-R


CASE #2 RedHat 7.2 KDE 2.2

1.
edit file /etc/profile
add to end of file:
export LANG=ru_RU.KOI8-R
export LC_ALL=ru_RU.KOI8-R

then Reboot Linux

2.
KDE Control Center -> Look&Feel -> Fonts
set character set for all fronts to KOI8-R

3.
KDE Control Center -> Personalization -> Country & Language
set Charset to KOI8-R

4.
KDE Control Center -> Peripherals -> Keyboard
turn on Additional layout "Russian". Check that U.S.English is added too

5.
PhpEd -> Settings -> Editor
set Character set to KOI8-R


CP1251 case
in case of CP1251, set up LC_ALL as ru_RU.CP1251,
but PhpEd should be set with font code page KOI8-R. See Settings -> Editor, Code page.