Japanese in Ubuntu

1. sudo apt-get install uim anthy scim-gtk2-immodule scim-uim

2. in /etc/X11/Xsession.d/

create: 78japanese_ime:

export XMODIFIERS="@im=SCIM"

export GTK_IM_MODULE="scim"

export XIM_PROGRAM="scim -d"

export QT_IM_MODULE="scim"

3. sudo dpkg-reconfigure locales

4. It is recommendable to install additional Japanese fonts.

UPDATE: I tried my method in KDE but it didn't work, so I found out that you may require to install one more package:

sudo apt-get install scim-bridge

Then, edit the file /etc/X11/xinit/xinput.d/scim and replace the value of "GTK_IM_MODULE" and "QT_IM_MODULE" from "xim" to "scim-bridge".

Your file may look like this:

XIM=SCIM
XIM_PROGRAM=/usr/bin/scim
XIM_ARGS="-d"
XIM_PROGRAM_SETS_ITSELF_AS_DAEMON=yes
GTK_IM_MODULE="scim-bridge"
QT_IM_MODULE="scim-bridge"
DEPENDS="scim,scim-anthy|scim-canna|scim-chewing|scim-pinyin|scim-hangle|scim-prime|scim-skk|scim-tables-additional|scim-m17n|scim-u
im|scim-tables-ja|scim-tables-ko|scim-tables-zh"

Japanese in Php:

[mbstring]
mbstring.language = Japanese
; you may want to change this encoding according to your preference
mbstring.internal_encoding = UTF-8
; this is important to be able to manipulate coding in forms.
mbstring.http_input = pass
; also you can modify this encoding to EUC-JP / Shift_JIS / ISO-2022-JP / UTF-16
mbstring.http_output = UTF-8
mbstring.detect_order = auto
mbstring.substitute_character = none;

define (CHARSET,"EUC-JP");
header("Content-Type: text/html; charset=".CHARSET);

function utf2code($utf){
    $full_code = "";
    for($mbl = 0; $mbl < mb_strlen($utf); $mbl++){
        $kanji = mb_substr($utf,$mbl,1);
        $len = strlen($kanji);
        for($ul=0;$ul<$len;$ul++){
           $k[$ul] = ord(substr($kanji,$ul,1));
        }
        switch($len){
           case 1: $code = $k[0]; break;
           case 2: $code = ((($k[0]-192)<<6)+$k[1]-128); break;
           case 3: $code = ((($k[0]-224)<<12)+(($k[1]-128)<<6)+$k[2]-128); break;
           case 4: $code = ((($k[0]-240)<<18)+(($k[1]-128)<<12)+(($k[2]-128)<<6)+$k[3]-128); break;
        }
        if($code > 0) $full_code .= "&#".$code.";";
}   
    return $full_code;
}