For this, you will need Regular Expressions and the preg_match function.
Something like:
if(preg_match('(bad|naughty)', $data) === 1) { }
The reason your attempt didn’t work
Regular Expressions are parsed by the PHP regex engine. The problem with your syntax is that you used the || operator. This is not a regex operator, so it is counted as part of the string.
As correctly stated above, if it’s counted as part of the string you’re looking to match: 'bad || naughty' as a string, rather than an expression!