# Example of THELUHNMOD-10 of credit card checkpoint algorithm implemented by php

Source: Internet
Author: User
This article mainly introduces the example of php implementation of the credit card check bit algorithm THELUHNMOD-10, friends can refer to the next

According to The Luhn Mod-10 Method of The payment card check bit algorithm in ISO 2894:

1. Multiply each digit on the card number by the weight. The rule is that if the number of card numbers is an even number, the first digit is multiplied by 2; otherwise, the number is multiplied by 1, and then the numbers are, 1, 2, 1, 2;
2. If each digit is multiplied by 9 after the weight, 9 is subtracted;
3. sum all processed weighted numbers and calculate the modulus using number 10;
4. The remainder must be 0. Otherwise, the input may be incorrect. It may also be a fake number.
With the simple implementation of PHP, front-end verification is better in actual scenarios, such as JS.

The Code is as follows:

Function check_card (\$ card ){
If (! Is_numeric (\$ card) return False;
\$ Card_len = strlen (\$ card );
\$ I = 0;
\$ Num_ I = array ();
Do {
If (! \$ I ){
\$ Num_x = \$ card_len % 2? 1: 2;
} Else {
\$ Num_x = 1? 2: 1;
}
\$ Num_ I [\$ I] = (int) \$ card [\$ I] * \$ num_x;
\$ Num_ I [\$ I] = \$ num_ I [\$ I]> 9? \$ Num_ I [\$ I]-9: \$ num_ I [\$ I];

} While (isset (\$ card [++ \$ I]);
\$ Num_sum = array_sum (\$ num_ I );
Return \$ num_sum % 10? False: True;
}

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