Check credit card type

credit_card.php

<?php

/**
 * Validates a credit card number using an array of approved card types.
 *
 * @param $number
 *   The credit card number to validate.
 * @param $card_types
 *   An array of credit card types containing any of the keys from the array
 *   returned by commerce_payment_credit_card_types(). Only numbers determined
 *   to be of the types specified will pass validation. This determination is
 *   based on the length of the number and the valid number ranges for the
 *   various types of known credit card types.
 *
 * @return
 *   FALSE if a number is not valid based on approved credit card types or the
 *   credit card type if it is valid and coud be determined.
 *
 * @see http://en.wikipedia.org/wiki/Bank_card_number#Issuer_Identification_Number_.28IIN.29
 * @see commerce_payment_credit_card_types()
 */
function commerce_payment_validate_credit_card_type($number, $card_types) {
  $strlen = strlen($number);

  // Provide a check on the first digit (and card length if applicable).
  switch (substr($number, 0, 1)) {
    case '3':
      // American Express begins with 3 and is 15 numbers.
      if ($strlen == 15 && in_array('amex', $card_types)) {
        return 'amex';
      }

      // JCB begins with 3528-3589 and is 16 numbers.
      if ($strlen == 16 && in_array('jcb', $card_types)) {
        return 'jcb';
      }

      // Carte Blanche begins with 300-305 and is 14 numbers.
      // Diners Club International begins 36 and is 14 numbers.
      if ($strlen == 14) {
        $initial = (int) substr($number, 0, 3);

        if ($initial >= 300 && $initial <= 305 && in_array('cb', $card_types)) {
          return 'cb';
        }

        if (substr($number, 0, 2) == '36' && in_array('dci', $card_types)) {
          return 'dci';
        }
      }

      return FALSE;

    case '4':
      $initial = (int) substr($number, 0, 4);
      $return = FALSE;

      if ($strlen == 16) {
        // Visa begins with 4 and is 16 numbers.
        if (in_array('visa', $card_types)) {
          $return = 'visa';
        }

        // Visa Electron begins with 4026, 417500, 4256, 4508, 4844, 4913, or
        // 4917 and is 16 numbers.
        if (in_array($initial, array(4026, 4256, 4508, 4844, 4913, 4917)) || substr($number, 0, 6) == '417500') {
          $return = in_array('visaelectron', $card_types) ? 'visaelectron' : FALSE;
        }
      }

      // Switch begins with 4903, 4905, 4911, or 4936 and is 16, 18, or 19
      // numbers.
      if (in_array($strlen, array(16, 18, 19)) &&
        in_array($initial, array(4903, 4905, 4911, 4936))) {
        $return = in_array('switch', $card_types) ? 'switch' : FALSE;
      }

      return $return;

    case '5':
      // MasterCard begins with 51-55 and is 16 numbers.
      // Diners Club begins with 54 or 55 and is 16 numbers.
      if ($strlen == 16) {
        $initial = (int) substr($number, 0, 2);

        if ($initial >= 51 && $initial <= 55 && in_array('mastercard', $card_types)) {
          return 'mastercard';
        }

        if ($initial >= 54 && $initial <= 55 && in_array('dc', $card_types)) {
          return 'dc';
        }
      }

      // Switch begins with 564182 and is 16, 18, or 19 numbers.
      if (in_array('switch', $card_types) && substr($number, 0, 6) == '564182' &&
        in_array($strlen, array(16, 18, 19))) {
        return 'switch';
      }

      // Maestro begins with 5018, 5020, or 5038 and is 12-19 numbers.
      if (in_array('maestro', $card_types) && $strlen >= 12 && $strlen <= 19 &&
        in_array(substr($number, 0, 4), array(5018, 5020, 5038))) {
        return 'maestro';
      }

      return FALSE;

    case '6':
      // Discover begins with 6011, 622126-622925, 644-649, or 65 and is 16
      // numbers.
      if ($strlen == 16 && in_array('discover', $card_types)) {
        if (substr($number, 0, 4) == '6011' || substr($number, 0, 2) == '65') {
          return 'discover';
        }

        $initial = (int) substr($number, 0, 6);

        if ($initial >= 622126 && $initial <= 622925) {
          return 'discover';
        }

        $initial = (int) substr($number, 0, 3);

        if ($initial >= 644 && $initial <= 649) {
          return 'discover';
        }
      }

      // Laser begins with 6304, 6706, 6771, or 6709 and is 16-19 numbers.
      $initial = (int) substr($number, 0, 4);

      if (in_array('laser', $card_types) && $strlen >= 16 && $strlen <= 19 &&
        in_array($initial, array(6304, 6706, 6771, 6709))) {
        return 'laser';
      }

      // Maestro begins with 6304, 6759, 6761, or 6763 and is 12-19 numbers.
      if (in_array('maestro', $card_types) && $strlen >= 12 && $strlen <= 19 &&
        in_array($initial, array(6304, 6759, 6761, 6763))) {
        return 'maestro';
      }

      // Solo begins with 6334 or 6767 and is 16, 18, or 19 numbers.
      if (in_array('solo', $card_types) && in_array($strlen, array(16, 18, 19)) &&
        in_array($initial, array(6334, 6767))) {
        return 'solo';
      }

      // Switch begins with 633110, 6333, or 6759 and is 16, 18, or 19 numbers.
      if (in_array('switch', $card_types) && in_array($strlen, array(16, 18, 19)) &&
        (in_array($initial, array(6333, 6759)) || substr($number, 0, 6) == 633110)) {
        return 'switch';
      }

      return FALSE;
  }

  return FALSE;
}

/**
 * Validates a credit card number using the Luhn algorithm.
 *
 * @param $number
 *   The credit card number to validate.
 *
 * @return
 *   TRUE or FALSE indicating the number's validity.
 *
 * @see http://www.merriampark.com/anatomycc.htm
 */
function commerce_payment_validate_credit_card_number($number) {
  // Ensure every character in the number is numeric.
  if (!ctype_digit($number)) {
    return FALSE;
  }

  // Validate the number using the Luhn algorithm.
  $total = 0;

  for ($i = 0; $i < strlen($number); $i++) {
    $digit = substr($number, $i, 1);
    if ((strlen($number) - $i - 1) % 2) {
      $digit *= 2;
      if ($digit > 9) {
        $digit -= 9;
      }
    }
    $total += $digit;
  }

  if ($total % 10 != 0) {
    return FALSE;
  }

  return TRUE;
}