$message_sous_forme_de_chaine = http_build_query($postfeilds);

//... début du code

$ch = curl_init();

//formatage de la chaine

foreach($postfeilds as $id=>$value)
{
$message_sous_forme_de_chaine.="$id=$value&";
}
//on enlève le dernier & qui est en trop
$message_sous_forme_de_chaine=substr($message_sous_forme_de_chaine,0,strlen($message_sous_forme_de_chaine)-1);

curl_setopt( $ch, CURLOPT_URL, $url);
curl_setopt( $ch, CURLOPT_HEADER, FALSE );
curl_setopt( $ch, CURLOPT_RETURNTRANSFER, TRUE );
curl_setopt( $ch, CURLOPT_POST, TRUE );
curl_setopt( $ch, CURLOPT_POSTFIELDS, $message_sous_forme_de_chaine);

curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);//!!!!!! à mettre absoluement sinon, la liste de certificats existants ne sera pas prise en compte
curl_setopt($ch, CURLOPT_REFERER, $referer);
$returned = curl_exec($ch);
curl_close($ch);
echo"$returned";

curl_setopt($ch, CURLOPT_REFERER, $referer);  

//... début du code

$ch = curl_init();
//formatage de la chaine
$message_sous_forme_de_chaine="";

foreach($postfields as id=>value)
{
$message_sous_forme_de_chaine.="$id=$value&";
}
//on enlève le dernier & qui est en trop
$message_sous_forme_de_chaine=substr($message_sous_forme_de_chaine,0,strlen($message_sous_forme_de_chaine)-1);

curl_setopt( $ch, CURLOPT_URL, $url_de_traitement_de_formulaire );
curl_setopt( $ch, CURLOPT_HEADER, FALSE );
curl_setopt( $ch, CURLOPT_RETURNTRANSFER, TRUE );
curl_setopt( $ch, CURLOPT_POST, TRUE );
curl_setopt( $ch, CURLOPT_POSTFIELDS, $message_sous_forme_de_chaine);

curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);//!!!!!! à mettre absoluement sinon, la liste de certificats existants ne sera pas prise en compte

$returned = curl_exec($ch);
curl_close($ch);

//...fin du code

$postfields = array();
$postfields["ssl_merchant_id"] = "mon code";
$postfields["ssl_user_id"] = "mon code";
$postfields["ssl_pin"] = "mon nip";
$postfeilds["ssl_test_mode"]="TRUE";  
$postfeilds["ssl_transaction_type"]="ccsale";
$postfeilds["ssl_card_number"]="$trnCardNumber";
$postfeilds["ssl_exp_date"]="$exp_date";
$postfeilds["ssl_amount"]="$montant";;
$postfeilds["ssl_show_form"]="false";
$postfeilds["ssl_email"]="$ssl_email";
$postfeilds["ssl_description"]="$ssl_description";
$postfeilds["ssl_cvv2cvc2_indicator"]="present"; //--CVV2 Indicator
$postfeilds["ssl_cvv2cvc2"]="$trnCardCvd"; //--CVV2 Data
$postfeilds["ssl_avs_address"]="$ssl_avs_adress2"; //AVS Postal Address
$postfeilds["ssl_avs_zip"]="$ssl_avs_zip";//--AVS ZIP Code --;
$postfeilds["ssl_invoice_number"]="$ssl_invoice_number";
$postfeilds["ssl_result_format"]="HTML";
$postfeilds["ssl_receipt_decl_method"]="REDG";
$postfeilds["ssl_receipt_decl_get_url"]="https://www.monsite.ca/decline.php";
$postfeilds["ssl_receipt_apprvl_method"]="REDG";
$postfeilds["ssl_receipt_apprvl_get_url"]="https://www.monsite.ca/confirm_insc.php";

$url = "https://www.myvirtualmerchant.com/VirtualMerchant/process.do"; //argument action dans form
$useragent = "Mozilla/5.0";
$referer = "https://www.monsite.ca/send_info_curl.php"; 
 
//Initialise une session CURL
$ch = curl_init($url);
//CURL options
curl_setopt($ch, CURLOPT_POST, 1);
//On poste les données du tableau $postfields
curl_setopt($ch, CURLOPT_POSTFIELDS, $postfields);
//On définit un useragent ici Mozilla/5.0
//souvent les bots se font passés pour googlebot ce qui finalement est stupide
//On passe donc un useragent banal
curl_setopt($ch, CURLOPT_USERAGENT, $useragent);
//On passe un referrer ici on passe la même page $url
curl_setopt($ch, CURLOPT_REFERER, $referer);
//on récupère le contenu de la page de résultat de la soumission dans une chaine
//curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
// en cas de redirection (facultatif ici)
//curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
//Page de résultats et fermeture de session
//$result = 
curl_exec($ch);
curl_close($ch);