I can' t get email with Facebook Login

Question

I want you to help me about Facebook login and GraphAPI.

I incorporate Facebook login with PHP SDK. I wrote like below.

$fb->get('/me?fields=first_name,last_name,email', $accessToken);

But I can't get user's email.

I tried below:

1st, I checked if I get AccessToken : Yes I debugged, and could get first_name, last_name.

2nd, In the first place, my code is right or not : Yes. I used GraphAPI explorer and got email.

3rd, I accessed some web pages and used facebook login. In my account, I saw my email and profiles are accessed. But my app doesn't get my email.(but my profile.)

Could you tell me why My app can't get email and How to fix? Please.