I see 2 things wrong here, perhaps that's why:
PHP Code:
new tarih[64];
get_time("%m/%d/%Y", tarih, charsmax(tarih));
log_to_file("addons/amxmodx/purpo_attack_log/%s.log", "%s", tarih, arg);
1. You're trying to use slashes in filename, which is not possible, since they are used for separating directories.
2. You're trying to format both the file name and the message in log_to_file (?), although it's possible only for the message.
Try replacing it with this:
PHP Code:
new tarih[64];
get_time("addons/amxmodx/purpo_attack_log/%Y-%m-%d.log", tarih, charsmax(tarih));
log_to_file(tarih, arg);