As explained in the issue, the dot notation can lead to invalid paths when used with some identifiers (for example, when it contains a -). The issue gives the following example:

use Symfony\Component\JsonPath\JsonCrawler;
use Symfony\Component\JsonPath\JsonPath;

$jsonPathExpression = (string) (new JsonPath)->key('some-prop');

dump((new JsonCrawler('{"some-prop": "example value"}'))->find($jsonPathExpression));

Let's always use the brackets notation in JsonPath::key(). Dot notation is only a shorthand to the verbose brackets version and this solves the problem without having to do further analysis on the key.

Added a few tests to ensure the brackets notation works well too.