How does PHP verify whether the entered bank card is valid?-php Tutorial

PHP: how to verify whether the entered bank card is valid? I am currently making an error entry. when I enter a bank card, I want to verify whether the bank card is valid, it is like an ID card. if you can verify whether the character string meets the requirements, find the complete code! I heard that there is a luhn algorithm, but this seems incomplete. Who gave me a function PHP that can be used immediately? how can I verify whether the bank card I entered is valid?
How does PHP verify whether the entered bank card is valid? when I enter a bank card for a lost object, I want to verify whether the bank card is valid like an ID card, can verify whether the string matches, please find the complete code! I heard that there is a luhn algorithm, but this seems incomplete. Who will give me a function that can be used right away?

Php, code, verification, bank card

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------ Solution --------------------
The LUHN algorithm is mainly used to calculate the validity of credit card and other document numbers.
1. starting from the last digit of the card number, multiply the even digit by 2. if the result is two digits, add and save the two digits.
2. add all numbers to get the sum.
3. if the credit card number is valid, the sum can be divided by 10.

Therefore

Function luhn ($ s ){
$ N = 0;
For ($ I = strlen ($ s)-1; $ I >=0; $ I --){
If ($ I % 2) $ n + = $ s {$ I };
Else {
$ T = $ s {$ I} * 2;
If ($ t> 9) $ t = $ t {0} + $ t {1 };
$ N + = $ t;
}
}
Return ($ n % 10) = 0;
}