If scope is different than 1, you will send the message without passing any arguments.
PHP Code:
message_begin(MSG_ONE,get_user_msgid("SetFOV"), .player=id);
if(scope[id] == 1)
write_byte(55);
message_end();
Make the check surround the whole message code instead:
PHP Code:
if(scope[id] == 1) {
message_begin(MSG_ONE,get_user_msgid("SetFOV"), .player=id);
write_byte(55);
message_end();
}