检查json对象的名称是否等于某个东西

So I have a basic json file:

{
    "User1": {
        "id": 1,
        ....
    },
    "User2": {
        "id": 3
        ....
    }
}

I want to get all the names of the users (i.e. "User1" or "User2") and check if a name entered by a user is equal to one of those names.

I've tried this but it doesn't work:

foreach($this->blackList as $user) {
    if($user == $username)
        return "TRUE";
    }
    return "FALSE";
}

I don't think you need to loop at all:

return array_key_exists($username, $this->blackList);

Or if you have json_decoded to an object instead of an array:

return property_exists($this->blackList, $username);

I assume that $this->blackList is decoded your json string. If yes, then code should look like this:

foreach($this->blackList as $blackName => $user) {
    if($blackName == $username)
        return true;
    }

}
return false;