<?php  

////////////////////////////////////////////////////  
//                                                //   
// Credit card validation routine                 //  
// May 15, 2000                                   //  
// By ariso                                       //  
// validateCardCode($number[,$cardtype])          //  
////////////////////////////////////////////////////  


function validateCardCode($cardnumber, $cardtype =  'unknown')
{  
     //Clean up input  

    $cardtype = strtolower($cardtype);  
    $cardnumber = ereg_replace( '[-[:space:]]',  '',$cardnumber);   

     //Do type specific checks  

    if ($cardtype ==  'unknown') {  
         //Skip type specific checks  
    }  
    elseif ($cardtype ==  'mastercard'){  
        if (strlen($cardnumber) != 16 || !ereg( '5[1-5]', $cardnumber)) return 0;  
    }  
    elseif ($cardtype ==  'visa'){  
        if ((strlen($cardnumber) != 13 && strlen($cardnumber) != 16) || substr($cardnumber, 0, 1) !=  '4')  

return 0;  
    }  
    elseif ($cardtype ==  'amex'){  
        if (strlen($cardnumber) != 15 || !ereg( '3[47]', $cardnumber)) return a;  
    }  
    elseif ($cardtype ==  'discover'){  
        if (strlen($cardnumber) != 16 || substr($cardnumber, 0, 4) !=  '6011') return 0;  
    }  
    else {  
         //invalid type entered  
        return -1;  
    }  

     // Start MOD 10 checks  

    $dig = toCharArray($cardnumber);  
    $numdig = sizeof ($dig);  
    $intIntJ = 0;  
    for ($intI=($numdig-2); $intI>=0; $intI-=2){  
        $dbl[$intIntJ] = $dig[$intI] * 2;  
        $intIntJ++;  
    }      
    $dblsz = sizeof($dbl);  
    $validate =0;  
    for ($intI=0;$intI<$dblsz;$intI++){  
        $add = toCharArray($dbl[$intI]);  
        for ($intIntJ=0;$intIntJ<sizeof($add);$intIntJ++){  
            $validate += $add[$intIntJ];  
        }  
    $add =  '';  
    }  
    for ($intI=($numdig-1); $intI>=0; $intI-=2){  
        $validate += $dig[$intI];   
    }  
    if (substr($validate, -1, 1) ==  '0') return 1;  
    else return 0;  
}  

// takes a string and returns an array of characters  

function toCharArray($intInput){  
    $len = strlen($intInput);  
    for ($intIntJ=0;$intIntJ<$len;$intIntJ++){  
        $char[$intIntJ] = substr($intInput, $intIntJ, 1);      
    }  
    return ($char);  
}  
?>