How to verify the validity of a bank card number using regular expressions in PHP

With the frequent use of bank cards in people's daily lives, the validity of bank card numbers has become an important issue. To ensure payment security, the validity of the bank card number must be verified. This article will introduce how to use regular expressions in PHP to verify the validity of bank card numbers.

1. The structure of bank card numbers

Before formally introducing how to use regular expressions to verify the validity of bank card numbers, we need to first understand the structure of bank card numbers. Generally speaking, a bank card number consists of the following parts:

1. Card issuing bank code: The card issuing bank code usually consists of 6 digits and is used to identify the institution that issued the bank card.

2. Account ID: The account ID usually consists of 1 to 19 digits and is used to identify the uniqueness of the bank card account.

3. Verification code: The verification code usually consists of 1 digit and is used to verify the validity of the bank card number.

2. Use regular expressions to verify the validity of bank card numbers

After understanding the structure of bank card numbers, we can use regular expressions to verify the validity of bank card numbers. . The specific verification method is as follows:

1. Use regular expressions to match bank card numbers.

Bank card numbers usually consist of 16 to 19 digits, so we can use the following regular expression to match:

/^[1-9]d{15,18}$/

The meaning of this regular expression is: starting with the numbers 1 to 9, followed by 15 to 18 digits, the entire string needs to match the entire expression.

2. Calculate whether the bank card number is valid through the check digit.

The check digit of the bank card number can be calculated by the Luhn algorithm. The specific calculation method is as follows:

(1) Multiply each digit by two from right to left.

(2) Add the ones and tens digits of numbers whose product is greater than 9 to get a new number.

(3) Add all the numbers to get a sum.

(4) If the sum is divisible by 10, the bank card number is valid, otherwise it is invalid.

The following is an example of using PHP code to verify bank card numbers:

function validate_bank_card($bank_card_number) {

if(!preg_match('/^[1-9]d{15,18}$/',$bank_card_number)) {
    return false;
}
$arr_card_number = str_split(strrev($bank_card_number));
$last_number_is_odd = false;
$total = 0;
foreach ($arr_card_number as $key => $value) {
    $num = intval($value);
    if ($last_number_is_odd) {
        $num *= 2;
        $num %= 10;
        $total += $num;
        $last_number_is_odd = false;
    } else {
        $total += $num;
        $last_number_is_odd = true;
    }
}
return ($total % 10) == 0;

}

The above code will Returns a Boolean value, true if the bank card number is valid, false otherwise.

3. Summary

The above is a detailed introduction on how to use regular expressions to verify the validity of bank card numbers in PHP. Validity verification of bank card numbers is one of the important measures for payment security, so this issue is very important. Using regular expressions to verify the validity of bank card numbers is a very simple, fast, and reliable method, and should be widely used when developing payment-related websites or applications.

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