↓こんなかんじ。超強引www

$ find . -name '*.php' | xargs nkf --overwrite -w -Lu
$ find . -name '*.htm' | xargs nkf --overwrite -w -Lu
$ find . -name '*.php' -type f -print | xargs perl -p -i -e "s/mb_convert_encoding\(/dummy_mb_convert_encoding(/g"
$ find . -name '*.php' -type f -print | xargs perl -p -i -e "s/mb_convert_variables\(/\/\/mb_convert_variables(/g"
$ perl -p -i -e 's/^<\?php/<?php\nfunction dummy_mb_convert_encoding(\$str, \$to = null, \$from = null) { return \$str; }/g' common.php
$ find . -name '*.php' -type f -print | xargs perl -p -i -e "s/shift_jis/UTF-8/g"