何度もすみません。
トリガー登録できない時は下記エラーが表示されます。

[ERROR: Cannot add trigger]
Incorrect trigger expression. [{localhost:eventlog[security].str(ƒGƒ‰[)}=1]

mbstringの設定というのはこれのことでしょうか？
[mbstring]
; language for internal character representation.
;mbstring.language = Japanese

; internal/script encoding.
; Some encoding cannot work as internal encoding.
; (e.g. SJIS, BIG5, ISO-2022-*)
;mbstring.internal_encoding = EUC-JP

; http input encoding.
;mbstring.http_input = auto

; http output encoding. mb_output_handler must be
; registered as output buffer to function
;mbstring.http_output = SJIS

; enable automatic encoding translation according to
; mbstring.internal_encoding setting. Input chars are
; converted to internal encoding by setting this to On.
; Note: Do _not_ use automatic encoding translation for
; portable libs/applications.
;mbstring.encoding_translation = Off

; automatic encoding detection order.
; auto means
;mbstring.detect_order = auto

; substitute_character used when character cannot be converted
; one from another
;mbstring.substitute_character = none;

; overload(replace) single byte functions by mbstring functions.
; mail(), ereg(), etc are overloaded by mb_send_mail(), mb_ereg(),
; etc. Possible values are 0,1,2,4 or combination of them.
; For example, 7 for overload everything.
; 0: No overload
; 1: Overload mail() function
; 2: Overload str*() functions
; 4: Overload ereg*() functions
;mbstring.func_overload = 0

; enable strict encoding detection.
;mbstring.strict_encoding = Off

よろしくお願いします。