Undefined index HTTP_HOST even though it is checked

Question

Here\'s the code:

if (isset($_SERVER[\'HTTP_HOST\']) === TRUE) {
  $host = $_SERVER[\'HTTP_HOST\'];
}

How is it possible to get an \"Undefined

Answer 1

When a request is done with an empty host:

GET / HTTP/1.1
Host:

Then isset($_SERVER['HTTP_HOST']) is true!

It is better to use empty like:

$host = '';
if (!empty($_SERVER['HTTP_HOST'])) {
  $host = $_SERVER['HTTP_HOST'];
}

For detailed info take a look here https://shiflett.org/blog/2006/server-name-versus-http-host