How to write regular expression validation for characters that should not be present?

Question

PHP

Hello, already the brain refuses from fatigue, but it is necessary to add the validation of the fields. How to correctly check the field for the presence of prohibited characters in any part of the word? No matter what I tried, it doesn't work...

Answer 1

Why is this regular? Use the native PHP function strpbrk()
As an example:

$illegal = "#$%^&*()+=-[]';,./{}|:<>?~";
$my_string = "Hello & World";
echo (false === strpbrk($my_string, $illegal)) ? 'Allowed' : "Disallowed";

Well, or, if you really want a regular, then like this:

return preg_match('/[#$%^&*()+=\-\[\]\';,.\/{}|":<>?~\\\\]/', $string);