i want check input by regex | contain 16 number

I have input, I want to check it.

It should accept only numbers, and must be 16, no more and no less.

How I can do that using php and regex?

Regex would be ^\d{16}$

preg_match("/^\\d{16}$/", $str);

^\d{16}$

Explication:

• ^ for the beginning of the line (so nothing before that)
• \d meaning a number (decimbal)
• {16} to mean "exactly 16"
• $ for the ending of the line (so nothing after that)

I think you need it for the credit card validator

^(\d{4}[- ]){3}\d{4}|\d{16}$

this will match :

1234-1234-1234-1234 | 1234 1234 1234 1234 | 1234123412341234

Please note that this is copied from regexlib

Would it not be better to make sure its 16 characters and numbers only with is_numeric() and strlen().