Contact Form 7 : How to create a custom URL validation

In WordPress, the Contact Form 7 is one of the most popular plugins for creating contact forms. One thing that you might have noticed though is that the validation of the URL field will not fail when you expect them to fail. For example, with the URL value of http://xxxx, the plugin will consider this as a valid URL, even though, the URL value is missing top-level domain part. The solution to this problem is to have a custom validation for the URL field. This article will show you how to achieve that.