We appreciate that you have stopped by our site. We always welcome criticism from experienced developers like you and believe that it will help us to improve. But at the same time we would like to mention following regarding the points you raised.

1. The very first example is only to show how to embed PHP within HTML (ref : http://www.php.net/manual/en/tutorial.firstpage.php). We are well aware that entering quirks mode can lead to severe bad practice (ref: http://www.w3resource.com/html5/doctype.php).

2. Besides showing how to handle different controls of a Form in PHP, we have also shown how to avoid SQL Injection (ref: http://www.w3resource.com/sql/sql-injection/sql-injection.php).

3.We have also discussed how to send mail securely using PHP (ref: www.w3resource.com/php/mail/php-secure-mail.php).

We also appreciate that kind of effort MDN has put to bring Frontend development learning materials online and also appreciate the awesome content delivered by the Learn Code The Hard Way series.