The first 4–6 digits that identify the card type and issuing bank.
Here is a simplified example of how you can implement this logic in PHP. This script takes a card number as input and returns whether it is mathematically valid. cc checker script php
9) { $digit -= 9; } } $sum += $digit; } return ($sum % 10 == 0); } // Example Usage $testCard = "4111111111111111"; // Standard Visa Test Number if (validateCC($testCard)) { echo "This is a mathematically valid card number."; } else { echo "Invalid card number."; } ?> Use code with caution. Key Features to Include in Your Script The first 4–6 digits that identify the card