<?php
/*
 *   This function validates a Spanish identification number
 *   verifying its check digits.
 *
 *   NIFs and NIEs are personal numbers.
 *   CIFs are corporates.
 *
 *   This function requires:
 *       - isValidCIF and isValidCIFFormat
 *       - isValidNIE and isValidNIEFormat
 *       - isValidNIF and isValidNIFFormat
 *
 *   This function returns:
 *       TRUE: If specified identification number is correct
 *       FALSE: Otherwise
 *
 *   Usage:
 *       echo isValidIdNumber( 'G28667152' );
 *   Returns:
 *       TRUE
 */

function isValidIdNumber($docNumber)
{
    $fixedDocNumber = strtoupper($docNumber);

    if (isValidNIFFormat($fixedDocNumber)) {
        return isValidNIF($fixedDocNumber);
    } else {
        if (isValidNIEFormat($fixedDocNumber)) {
            return isValidNIE($fixedDocNumber);
        } else {
            if (isValidCIFFormat($fixedDocNumber)) {
                return isValidCIF($fixedDocNumber);
            } else {
                return FALSE;
            }
        }
    }
}
/*
 *   This function validates a Spanish identification number
 *   verifying its check digits.
 *
 *   This function is intended to work with NIF numbers.
 *
 *   This function is used by:
 *       - isValidIdNumber
 *
 *   This function requires:
 *       - isValidCIFFormat
 *       - getNIFCheckDigit
 *
 *   This function returns:
 *       TRUE: If specified identification number is correct
 *       FALSE: Otherwise
 *
 *   Algorithm works as described in:
 *       http://www.interior.gob.es/dni-8/calculo-del-digito-de-Check-del-nif-nie-2217
 *
 *   Usage:
 *       echo isValidNIF( '33576428Q' );
 *   Returns:
 *       TRUE
 */

function isValidNIF($docNumber)
{
    $isValid        = FALSE;
    $fixedDocNumber = "";

    $correctDigit = "";
    $writtenDigit = "";

    if (!preg_match("/^[A-Z]+$/i", substr($fixedDocNumber, 1, 1))) {
        $fixedDocNumber = strtoupper(substr("000000000".$docNumber, -9));
    } else {
        $fixedDocNumber = strtoupper($docNumber);
    }

    $writtenDigit = substr($docNumber, -1, 1);

    if (isValidNIFFormat($fixedDocNumber)) {
        $correctDigit = getNIFCheckDigit($fixedDocNumber);

        if ($writtenDigit == $correctDigit) {
            $isValid = TRUE;
        }
    }

    return $isValid;
}
/*
 *   This function validates a Spanish identification number
 *   verifying its check digits.
 *
 *   This function is intended to work with NIE numbers.
 *
 *   This function is used by:
 *       - isValidIdNumber
 *
 *   This function requires:
 *       - isValidNIEFormat
 *       - isValidNIF
 *
 *   This function returns:
 *       TRUE: If specified identification number is correct
 *       FALSE: Otherwise
 *
 *   Algorithm works as described in:
 *       http://www.interior.gob.es/dni-8/calculo-del-digito-de-control-del-nif-nie-2217
 *
 *   Usage:
 *       echo isValidNIE( 'X6089822C' )
 *   Returns:
 *       TRUE
 */

function isValidNIE($docNumber)
{
    $isValid        = FALSE;
    $fixedDocNumber = "";

    if (!preg_match("/^[A-Z]+$/i", substr($fixedDocNumber, 1, 1))) {
        $fixedDocNumber = strtoupper(substr("000000000".$docNumber, -9));
    } else {
        $fixedDocNumber = strtoupper($docNumber);
    }

    if (isValidNIEFormat($fixedDocNumber)) {
        if (substr($fixedDocNumber, 1, 1) == "T") {
            $isValid = TRUE;
        } else {
            /* The algorithm for validating the check digits of a NIE number is
              identical to the altorithm for validating NIF numbers. We only have to
              replace Y, X and Z with 1, 0 and 2 respectively; and then, run
              the NIF altorithm */

            $fixedDocNumber = str_replace('Y', '1', $fixedDocNumber);
            $fixedDocNumber = str_replace('X', '0', $fixedDocNumber);
            $fixedDocNumber = str_replace('Z', '2', $fixedDocNumber);

            $isValid = isValidNIF($fixedDocNumber);
        }
    }

    return $isValid;
}
/*
 *   This function validates a Spanish identification number
 *   verifying its check digits.
 *
 *   This function is intended to work with CIF numbers.
 *
 *   This function is used by:
 *       - isValidDoc
 *
 *   This function requires:
 *       - isValidCIFFormat
 *       - getCIFCheckDigit
 *
 *   This function returns:
 *       TRUE: If specified identification number is correct
 *       FALSE: Otherwise
 *
 * CIF numbers structure is defined at:
 *   BOE number 49. February 26th, 2008 (article 2)
 *
 *   Usage:
 *       echo isValidCIF( 'F43298256' );
 *   Returns:
 *       TRUE
 */

function isValidCIF($docNumber)
{
    $isValid        = FALSE;
    $fixedDocNumber = "";

    $correctDigit = "";
    $writtenDigit = "";

    $fixedDocNumber = strtoupper($docNumber);
    $writtenDigit   = substr($fixedDocNumber, -1, 1);

    if (isValidCIFFormat($fixedDocNumber) == 1) {
        $correctDigit = getCIFCheckDigit($fixedDocNumber);

        if ($writtenDigit == $correctDigit) {
            $isValid = TRUE;
        }
    }

    return $isValid;
}
/*
 *   This function validates the format of a given string in order to
 *   see if it fits with NIF format. Practically, it performs a validation
 *   over a NIF, except this function does not check the check digit.
 *
 *   This function is intended to work with NIF numbers.
 *
 *   This function is used by:
 *       - isValidIdNumber
 *       - isValidNIF
 *
 *   This function returns:
 *       TRUE: If specified string respects NIF format
 *       FALSE: Otherwise
 *
 *   Usage:
 *       echo isValidNIFFormat( '33576428Q' )
 *   Returns:
 *       TRUE
 */

function isValidNIFFormat($docNumber)
{
    return respectsDocPattern(
        $docNumber, '/^[KLM0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][A-Z0-9]/');
}
/*
 *   This function validates the format of a given string in order to
 *   see if it fits with NIE format. Practically, it performs a validation
 *   over a NIE, except this function does not check the check digit.
 *
 *   This function is intended to work with NIE numbers.
 *
 *   This function is used by:
 *       - isValidIdNumber
 *       - isValidNIE
 *
 *   This function requires:
 *       - respectsDocPattern
 *
 *   This function returns:
 *       TRUE: If specified string respects NIE format
 *       FALSE: Otherwise
 *
 *   Usage:
 *       echo isValidNIEFormat( 'X6089822C' )
 *   Returns:
 *       TRUE
 */

function isValidNIEFormat($docNumber)
{
    return respectsDocPattern(
        $docNumber, '/^[XYZT][0-9][0-9][0-9][0-9][0-9][0-9][0-9][A-Z0-9]/');
}
/*
 *   This function validates the format of a given string in order to
 *   see if it fits with CIF format. Practically, it performs a validation
 *   over a CIF, but this function does not check the check digit.
 *
 *   This function is intended to work with CIF numbers.
 *
 *   This function is used by:
 *       - isValidIdNumber
 *       - isValidCIF
 *
 *   This function requires:
 *       - respectsDocPattern
 *
 *   This function returns:
 *       TRUE: If specified string respects CIF format
 *       FALSE: Otherwise
 *
 *   Usage:
 *       echo isValidCIFFormat( 'H24930836' )
 *   Returns:
 *       TRUE
 */

function isValidCIFFormat($docNumber)
{
    return
        respectsDocPattern(
            $docNumber, '/^[PQSNWR][0-9][0-9][0-9][0-9][0-9][0-9][0-9][A-Z0-9]/')
        or
        respectsDocPattern(
            $docNumber, '/^[ABCDEFGHJUV][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]/');
}
/*
 *   This function calculates the check digit for an individual Spanish
 *   identification number (NIF).
 *
 *   You can replace check digit with a zero when calling the function.
 *
 *   This function is used by:
 *       - isValidNIF
 *
 *   This function requires:
 *       - isValidNIFFormat
 *
 *   This function returns:
 *       - Returns check digit if provided string had a correct NIF structure
 *       - An empty string otherwise
 *
 *   Usage:
 *       echo getNIFCheckDigit( '335764280' )
 *   Returns:
 *       Q
 */

function getNIFCheckDigit($docNumber)
{
    $keyString = 'TRWAGMYFPDXBNJZSQVHLCKE';

    $fixedDocNumber = "";

    $position      = 0;
    $writtenLetter = "";
    $correctLetter = "";

    if (!preg_match("/^[A-Z]+$/i", substr($fixedDocNumber, 1, 1))) {
        $fixedDocNumber = strtoupper(substr("000000000".$docNumber, -9));
    } else {
        $fixedDocNumber = strtoupper($docNumber);
    }

    if (isValidNIFFormat($fixedDocNumber)) {
        $writtenLetter = substr($fixedDocNumber, -1);

        if (isValidNIFFormat($fixedDocNumber)) {
            $fixedDocNumber = str_replace('K', '0', $fixedDocNumber);
            $fixedDocNumber = str_replace('L', '0', $fixedDocNumber);
            $fixedDocNumber = str_replace('M', '0', $fixedDocNumber);

            $position      = substr($fixedDocNumber, 0, 8) % 23;
            $correctLetter = substr($keyString, $position, 1);
        }
    }

    return $correctLetter;
}
/*
 *   This function calculates the check digit for a corporate Spanish
 *   identification number (CIF).
 *
 *   You can replace check digit with a zero when calling the function.
 *
 *   This function is used by:
 *       - isValidCIF
 *
 *   This function requires:
 *     - isValidCIFFormat
 *
 *   This function returns:
 *       - The correct check digit if provided string had a
 *         correct CIF structure
 *       - An empty string otherwise
 *
 *   Usage:
 *       echo getCIFCheckDigit( 'H24930830' );
 *   Prints:
 *       6
 */

function getCIFCheckDigit($docNumber)
{
    $fixedDocNumber = "";

    $centralChars = "";
    $firstChar    = "";

    $evenSum           = 0;
    $oddSum            = 0;
    $totalSum          = 0;
    $lastDigitTotalSum = 0;

    $correctDigit = "";

    $fixedDocNumber = strtoupper($docNumber);

    if (isValidCIFFormat($fixedDocNumber)) {
        $firstChar    = substr($fixedDocNumber, 0, 1);
        $centralChars = substr($fixedDocNumber, 1, 7);

        $evenSum = substr($centralChars, 1, 1) +
            substr($centralChars, 3, 1) +
            substr($centralChars, 5, 1);

        $oddSum = sumDigits(substr($centralChars, 0, 1) * 2) +
            sumDigits(substr($centralChars, 2, 1) * 2) +
            sumDigits(substr($centralChars, 4, 1) * 2) +
            sumDigits(substr($centralChars, 6, 1) * 2);

        $totalSum = $evenSum + $oddSum;

        $lastDigitTotalSum = substr($totalSum, -1);

        if ($lastDigitTotalSum > 0) {
            $correctDigit = 10 - ($lastDigitTotalSum % 10);
        } else {
            $correctDigit = 0;
        }
    }

    /* If CIF number starts with P, Q, S, N, W or R,
      check digit sould be a letter */
    if (preg_match('/[PQSNWR]/', $firstChar)) {
        $correctDigit = substr("JABCDEFGHI", $correctDigit, 1);
    }

    return $correctDigit;
}
/*
 *   This function validates the format of a given string in order to
 *   see if it fits a regexp pattern.
 *
 *   This function is intended to work with Spanish identification
 *   numbers, so it always checks string length (should be 9) and
 *   accepts the absence of leading zeros.
 *
 *   This function is used by:
 *       - isValidNIFFormat
 *       - isValidNIEFormat
 *       - isValidCIFFormat
 *
 *   This function returns:
 *       TRUE: If specified string respects the pattern
 *       FALSE: Otherwise
 *
 *   Usage:
 *       echo respectsDocPattern(
 *           '33576428Q',
 *           '/^[KLM0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][A-Z]/' );
 *   Returns:
 *       TRUE
 */

function respectsDocPattern($givenString, $pattern)
{
    $isValid = FALSE;

    $fixedString = strtoupper($givenString);

    if (is_int(substr($fixedString, 0, 1))) {
        $fixedString = substr("000000000".$givenString, -9);
    }

    if (preg_match($pattern, $fixedString)) {
        $isValid = TRUE;
    }

    return $isValid;
}
/*
 *   This function performs the sum, one by one, of the digits
 *   in a given quantity.
 *
 *   For instance, it returns 6 for 123 (as it sums 1 + 2 + 3).
 *
 *   This function is used by:
 *       - getCIFCheckDigit
 *
 *   Usage:
 *       echo sumDigits( 12345 );
 *   Returns:
 *       15
 */

function sumDigits($digits)
{
    $total = 0;
    $i     = 1;

    while ($i <= strlen($digits)) {
        $thisNumber = substr($digits, $i - 1, 1);
        $total += $thisNumber;

        $i++;
    }

    return $total;
}
?>