invoiceninja/app/models/Gateway.php

<?php

class Gateway extends Eloquent
{
    public $timestamps = true;
    protected $softDelete = false;

    public function paymentlibrary()
    {
        return $this->belongsTo('PaymentLibrary', 'payment_library_id');
    }

    public function getLogoUrl()
    {
        return '/images/gateways/logo_'.$this->provider.'.png';
    }

    public function getHelp()
    {
        $link = '';

        if ($this->id == GATEWAY_AUTHORIZE_NET || $this->id == GATEWAY_AUTHORIZE_NET_SIM) {
            $link = 'http://reseller.authorize.net/application/?id=5560364';
        } elseif ($this->id == GATEWAY_PAYPAL_EXPRESS) {
            $link = 'https://www.paypal.com/us/cgi-bin/webscr?cmd=_login-api-run';
        } elseif ($this->id == GATEWAY_TWO_CHECKOUT) {
            $link = 'https://www.2checkout.com/referral?r=2c37ac2298';
        }

        $key = 'texts.gateway_help_'.$this->id;
        $str = trans($key, ['link' => "<a href='$link' target='_blank'>Click here</a>"]);

        return $key != $str ? $str : '';
    }

    public function getFields()
    {
        $paymentLibrary =  $this->paymentlibrary;

        if ($paymentLibrary->id == PAYMENT_LIBRARY_OMNIPAY) {
            $fields = Omnipay::create($this->provider)->getDefaultParameters();
        } else {
            $fields = Payment_Utility::load('config', 'drivers/'.strtolower($this->provider));
        }

        if ($fields == null) {
            $fields = array();
        }

        return $fields;
    }
}