: Storing or even transmitting raw credit card data through a custom PHP script without proper encryption violates industry security standards.
: Checks if the number is mathematically valid (structure, length, and checksum). This does not require an internet connection or bank access. Transaction Authorization cc checker script php
; $i < strlen($reverse_num); $i++) $digit = (int)$reverse_num[$i]; // Double every second digit ) $digit -= ; : Storing or even transmitting raw credit card
$sum += $n; $alternate = !$alternate;
: Use regular expressions to identify the card brand (Visa, Mastercard, etc.) based on the leading digits. Visa : Starts with 4; length 13 or 16. Mastercard : Starts with 51–55; length 16. American Express : Starts with 34 or 37; length 15. $i $sum += $n
