Sign is with php missing id_token on authorization code

Hello.

Querying https://appleid.apple.com/auth/token gives back no id_token randomly.

I'm sending:
'grant_type' => 'authorization_code',
'client_id' => {client id},
'client_secret' => {client secret},
'code' => {authorization code},

Sometimes I have this:

• "access_token": {some string}

• "token_type": "Bearer"

• "expires_in": 3600

• "refresh_token": {some string}

and sometimes this:

• "access_token": {some string}

• "token_type": "Bearer"

• "expires_in": 3600

• "refresh_token": {some string}

• "id_token": {some string}

I don't understand why is not returning all the time. can you help me? I need that id_token