Quotes are to typecast PHP value into a string, because developer can give `5` and not `"5"` in `$value` parameter, which would fail to match with `==` used in JavaScript, since `getAttribute` in JavaScript always returns a string and type casting in JavaScript is not that superior as in PHP.

Basically `(string)$value` would have same effect, but I personally prefer to use double quotes, because it shorter to write.