This error message is telling you that you are using the constant index as if it were a string, but PHP is assuming that you meant the string 'index'. This is because you did not wrap the constant in quotes, which is required in PHP.
To fix this error, you need to wrap the constant in quotes, like this:
{{ url(‘index’) }}This will tell PHP that you meant to use the string 'index' instead of a constant with the name index.
