src/Core/OAuth/OAuth2/OAuth2AccessToken.php
public function getAccessTokenValidationPeriodInSeconds(){
      if(isset($this->accessTokenValidationPeriod) && !empty($this->accessTokenValidationPeriod))
      {
          return $this->accessTokenValidationPeriod;
      }else{
        throw new SdkException("The validation period for OAuth 2 access Token is not set.");
      }
    }
public function getAccessTokenValidationPeriodInSeconds(){
      if(isset($this->accessTokenValidationPeriod) && !empty($this->accessTokenValidationPeriod))
      {
          return $this->accessTokenValidationPeriod;
      }else{
        throw new SdkException("The validation period for OAuth 2 access Token is not set.");
      }
    }
Return the number of seconds for access token
The implementation of Quickbooks Online OAuth 2 always return an one hour access token. This method is not useful
@return int