src/Grant/PasswordGrant.php
protected function getVerifyCredentialsCallback()
    {
        if (is_null($this->callback) || !is_callable($this->callback)) {
            throw new Exception\ServerErrorException('Null or non-callable callback set on Password grant');
        }

        return $this->callback;
    }
protected function getVerifyCredentialsCallback()
    {
        if (is_null($this->callback) || !is_callable($this->callback)) {
            throw new Exception\ServerErrorException('Null or non-callable callback set on Password grant');
        }

        return $this->callback;
    }
protected function getVerifyCredentialsCallback ( ) { if ( is_null ( $ this -> callback ) || ! is_callable ( $ this -> callback ) ) { throw new Exception \ ServerErrorException ( 'Null or non-callable callback set on Password grant' ) ; } return $ this -> callback ; }
Return the callback function

@return callable

@throws
Return the callback function