使用PHP的Google AnalyticsAPI v3

I am using "Google Analytics API v3 with PHP" (https://github.com/wanze/Google-Analytics-API-PHP) using "Web applications" but I am getting following error.

array(2) {
  ["http_code"]=> int(401)
  ["error"]=> array(3) {
    ["errors"]=> array(1) {
      [0]=> array(5) {
        ["domain"]=> string(6) "global"
        ["reason"]=> string(9) "authError"
        ["message"]=> string(19) "Invalid Credentials"
        ["locationType"]=> string(6) "header"
        ["location"]=> string(13) "Authorization"
      }
    }
    ["code"]=> int(401)
    ["message"]=> string(19) "Invalid Credentials"
  }
} 

Please anyone reply for this one? Thanks