使用HTML5验证功能检查现有用户名

Question

I'm creating a registration form and I would like to check if the user already exist using PHP and HTML5 validation.

So somehow I would like to send the username that was typed in to a PHP function and write error message with setCustomValidity() in JavaScript (HTML5)

Can anyone offer me any advice to achieve this?

Answer 1

You can't do this automatically, if that's what you're asking. You'll need to provide validation on the server-side, too. HTML5 is client-side. And even if it did send usable validation parameters somehow, those could be falsified.

As for checking if a user already exists, this can't be done with HTML5. What you can do is client-side validation with Ajax.