sfValidator extension based on Credit Card Validator code by Harish Chauhan (from phpclasses.org). With this extension you can validate this type of credit cards: VISA, MASTERCARD, DISCOVER, AMEX, DINERS,JCB, Australian Bankcard, EnRoute And Switch Solo.

IMHO isn't a bad idea to include anything like this in standard sfValidator code. While here you have the source code of my adaptation of credit cards validator.

<?php
 
/*
 
Symfony integration as sfValidator of CCVAL
Date - Jun 17, 2006
Author - Oriol Rius (oriol@joor.net)
 
Credit CArd Validator
Date - Jan 14, 2005
Author - Harish Chauhan
 
 
ABOUT
This PHP script will calidate credit cards by checking there length
and pattern and checksum using mod 10.
 
Supported credit cards are VISA, MASTERCARD, DISCOVER, AMEX, DINERS,
JCB, Australian Bankcard, EnRoute And Switch Solo.
*/
 
class CCVAL extends sfValidator
{
 
    public function execute (&$value, &$error)
    {       
        // Recuperamos parámetros validar
        $num_param = $this->getParameterHolder()->get('num');
        $num = $this->getContext()->getRequest()->getParameter($num_param);
        $tipo_param = $this->getParameterHolder()->get('tipo');
        $tipo = $this->getContext()->getRequest()->getParameter($tipo_param);
 
        // Lanzamos la validación
        $validada=$this->_isVAlidCreditCard($num,$tipo,false);
 
        // Informamos de como ha ido la validación
        sfContext::getInstance()->getLogger()->info("CCVAL.class.php: Tipo: ".$tipo." Num: ".$num." Validada: ".$validada);             
 
        if ($validada==false)
        {
            $error = $this->getParameterHolder()->get('error');
            return false;
        }
        return true;
    }
 
    public function initialize ($context, $parameters = null)
    {
        // initialize parent
        parent::initialize($context);
 
        $this->getParameterHolder()->add($parameters);
 
        return true;
    }
 
    /**
     * Testing checksum
     *
     * @param integer $ccnum
     * @return boolean
     */
    private function _checkSum($ccnum)
    {
        $checksum = 0;
        for ($i=(2-(strlen($ccnum) % 2)); $i<=strlen($ccnum); $i+=2)
        {
            $checksum += (int)($ccnum{$i-1});
        }
        // Analyze odd digits in even length strings or even digits in odd length strings.
        for ($i=(strlen($ccnum)% 2) + 1; $i<strlen($ccnum); $i+=2)
        {
            $digit = (int)($ccnum{$i-1}) * 2;
            if ($digit < 10)
            { $checksum += $digit; }
            else
            { $checksum += ($digit-9); }
        }
        if (($checksum % 10) == 0)
        return true;
        else
        return false;
 
    }
 
    /**
     * Launch validation
     *
     * @param integer $ccnum
     * @param string $type
     * @param boolean $returnobj
     * @return boolean
     */
    private function _isVAlidCreditCard($ccnum,$type="",$returnobj=false)
    {
        $creditcard=array(  "visa"=>"/^4\d{3}-?\d{4}-?\d{4}-?\d{4}$/",
        "mastercard"=>"/^5[1-5]\d{2}-?\d{4}-?\d{4}-?\d{4}$/",
        "discover"=>"/^6011-?\d{4}-?\d{4}-?\d{4}$/",
        "amex"=>"/^3[4,7]\d{13}$/",
        "diners"=>"/^3[0,6,8]\d{12}$/",
        "bankcard"=>"/^5610-?\d{4}-?\d{4}-?\d{4}$/",
        "jcb"=>"/^[3088|3096|3112|3158|3337|3528]\d{12}$/",
        "enroute"=>"/^[2014|2149]\d{11}$/",
        "switch"=>"/^[4903|4911|4936|5641|6333|6759|6334|6767]\d{12}$/");
        if(empty($type))
        {
            $match=false;
            foreach($creditcard as $type=>$pattern)
            if(preg_match($pattern,$ccnum)==1)
            {
                $match=true;
                break;
            }
 
            if(!$match)
            return false;
            else
            {
                if($returnobj)
                {
                    $return=new stdclass;
                    $return->valid=$this->_checkSum($ccnum);
                    $return->ccnum=$ccnum;
                    $return->type=$type;
                    return $return;
                }
                else
                return $this->_checkSum($ccnum);
            }
 
        }
        else
        {
            if(@preg_match($creditcard[strtolower(trim($type))],$ccnum)==0)
            return false;
            else
            {
                if($returnobj)
                {
                    $return=new stdclass;
                    $return->valid=$this->_checkSum($ccnum);
                    $return->ccnum=$ccnum;
                    $return->type=$type;
                    return $return;
                }
                else
                return $this->_checkSum($ccnum);
            }
        }
    }
}
?>

An example of how you can call CCVAL validator from validate yml file:

methods:
  post: [ntarjeta]
names:
  ntarjeta:
    required:     Yes
    required_msg: Credit Card number is required
    validators:   validarCC
 
validarCC:
    class:       CCVAL
    param:
      num:       ntarjeta
      tipo:      tipoCC
      error:     Your credit card number is invalid

Sorry for my poor english.