Redirecting the buyer to the payment page

The URL of the payment gateway is:
https://secure.payzen.eu/vads-payment/
Example of parameters sent to the payment gateway:
<form method="POST" action="https://secure.payzen.eu/vads-payment/">
<input type="hidden" name="vads_action_mode" value="INTERACTIVE" /> 
<input type="hidden" name="vads_amount" value="2990" /> 
<input type="hidden" name="vads_ctx_mode" value="TEST" /> 
<input type="hidden" name="vads_currency" value="978" />
<input type="hidden" name="vads_cust_country" value="FR" />
<input type="hidden" name="vads_cust_email" value="nom.prenom@exemple.com" />
<input type="hidden" name="vads_page_action" value="PAYMENT" /> 
<input type="hidden" name="vads_payment_config" value="SINGLE" /> 
<input type="hidden" name="vads_site_id" value="12345678" /> 
<input type="hidden" name="vads_trans_date" value="20160526101407" /> 
<input type="hidden" name="vads_trans_id" value="362812" /> 
<input type="hidden" name="vads_version" value="V2" />
<input type="hidden" name="signature" value="28e0dd3ac1f38147717816dd65ff15cbf974f251"/>
<input type="submit" name="payer" value="Payer"/>
</form>