PHP Regex preg_match: Unknown modifier

Question

I'm trying to make a function that allows a string only certain characters, but it's not working. Here is my code:

$passRegex = '/[^A-Za-z0-9!\";#\$%&\'\(\)\*\+,-\./\:;<=>\?@\[]^_`\{\|}]/';

if(preg_match($passRegex, $str)) // invalid 

But it throws

Warning:  preg_match(): Unknown modifier '\'

This is the char list I want to allow:

!\";#$%&'()*+,-./:;<=>?@[]^_`{|}~0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ