php.ini の設定

アップロードに関係ありそうな項目
post_max_size
max_execution_time
memory_limit
upload_max_filesize

文字コードに関して
スクリプトの文字コードと出力がsift_jisの場合
output_buffering = Off
magic_quotes_gpc = Off
default_charset = Shift_JIS
mbstring.language = Japanese
mbstring.internal_encoding = SJIS
mbstring.http_input = auto
mbstring.http_output = SJIS
mbstring.encoding_translation = On
mbstring.detect_order = auto
mbstring.substitute_character = none

スクリプトの文字コードと出力がeuc_jpの場合
output_buffering = Off
magic_quotes_gpc = Off
default_charset = EUC-JP
mbstring.language = Japanese
mbstring.internal_encoding = EUC-JP
mbstring.http_input = auto
mbstring.http_output = EUC-JP
mbstring.encoding_translation = On
mbstring.detect_order = auto
mbstring.substitute_character = none