What are the considerations for handling validation of ISBN-10 and ISBN-13 numbers in PHP, including checksum validation?

When validating ISBN-10 and ISBN-13 numbers in PHP, it's important to consider the checksum validation to ensure the numbers are valid. For ISBN-10, the checksum is calculated using a weighted sum formula, while for ISBN-13, it uses a different algorithm. It's crucial to implement these checksum validations to ensure the integrity of the ISBN numbers. 

function validateISBN10($isbn) {
    $isbn = str_replace('-', '', $isbn);
    
    if (!preg_match('/^\d{9}[\dX]$/', $isbn)) {
        return false;
    }

    $sum = 0;
    for ($i = 0; $i < 9; $i++) {
        $sum += $isbn[$i] * (10 - $i);
    }

    $checksum = ($isbn[9] == 'X') ? 10 : $isbn[9];
    
    return $sum % 11 == $checksum;
}

function validateISBN13($isbn) {
    $isbn = str_replace('-', '', $isbn);

    if (!preg_match('/^\d{13}$/', $isbn)) {
        return false;
    }

    $sum = 0;
    for ($i = 0; $i < 12; $i++) {
        $sum += $isbn[$i] * (($i % 2 == 0) ? 1 : 3);
    }

    $checksum = 10 - $sum % 10;

    return $checksum == $isbn[12];
}

$isbn10 = '0684856093';
$isbn13 = '9780132350884';

echo validateISBN10($isbn10) ? 'Valid ISBN-10' : 'Invalid ISBN-10'; // Output: Valid ISBN-10
echo "\n";
echo validateISBN13($isbn13) ? 'Valid ISBN-13' : 'Invalid ISBN-13'; // Output: Valid ISBN-13

Keywords

ISBN-10 ISBN-13 validation checksum PHP

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