How to know if Access Token expires in Google Api PHP

Question

How will I know if my access token has expired.

I'm using try and catch

try {
$result = file_get_contents('https://www.googleapis.com/calendar/v3/calendars/primary/events?access_token='.$accesstoken);
print_r($result);
}
catch(Exception $e){
echo "Get new token";
}

but still it gets error from the file_get_contents then prints "Get new token"

If I want to use curl

$ch = curl_init();
curl_setopt($ch,CURLOPT_URL,'https://www.googleapis.com/calendar/v3/calendars/primary/events?access_token='.$accesstoken);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
$result = curl_exec($ch);
curl_close($ch);

then what should I do to catch the error here?

//if error because access token is invalid,
  do here

// my fixed solution

 $response= json_decode($result);
 if($response->error){ // if result has errors
   echo "Get new token";
 }

Answer 1

probing this url:

https://www.googleapis.com/oauth2/v1/tokeninfo?access_token={accessToken}

will gives you:

{
  "audience":<your_client_id>,
  "user_id":<user_id_if_userinfo.profile_was_authorized>,
  "scope":"<authorized_scope_1> <authorized_scope_1>",
  "expires_in":<time_to_live>
}

or an error:

{"error":"invalid_token"}

Answer 2

Catch the exceptions. Check if the HTTP error code is 401(unauthorized). This means that your access token has expired and its the time u refresh your access token.