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<?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);
}

?>