PHP Detect URL Protocol - http vs https

I've written a little function to establish the current site url protocol but I don't have SSL and don't know how to test if it works under https. Can you tell me if this is correct?

function siteURL()
{
    $protocol = (!empty($_SERVER['HTTPS']) && $_SERVER['HTTPS'] !== 'off' || $_SERVER['SERVER_PORT'] == 443) ? "https://" : "http://";
    $domainName = $_SERVER['HTTP_HOST'].'/';
    return $protocol.$domainName;
}
define( 'SITE_URL', siteURL() );

Is it necessary to do it like above or can I just do it like?:

function siteURL()
{
    $protocol = 'http://';
    $domainName = $_SERVER['HTTP_HOST'].'/'
    return $protocol.$domainName;
}
define( 'SITE_URL', siteURL() );

Under SSL, doesn't the server automatically convert the url to https even if the anchor tag url is using http? Is it necessary to check for the protocol?

Thank you!



Answer:
I know it's late, although there is a much more convenient way to solve this kind of problem! the solutions shown above are quite messy, and if someone should ever check back on this, there's how i would do:

$protocol = stripos($_SERVER['SERVER_PROTOCOL'],'https') === true ? 'https://' : 'http://';

or even without condition if you don t like

$protocol = strtolower(substr($_SERVER["SERVER_PROTOCOL"],0,strpos( $_SERVER["SERVER_PROTOCOL"],'/'))).'://';

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