PHP header redirect 301 – what are the implications

headerhttp-status-code-301PHPredirect

I have domain.com. If the user is logged in, it should load automatically domain.com/option-X where X is a predefined choice of the user.

So, I do this at the top of index.php:

header("Location: /option-X");

But, if the user is not logged in, I just choose automatically the first option like this:

header("HTTP/1.1 301 Moved Permanently"); 
header("Location: /option-a");

So, i have two questions regarding the implications of doing so:

Since the search engines crawlers won't be logged in, they will always get domain.com/option-a – does it affect them that it has a 301 header?
What could be the server cpu load of doing those redirects? I don't know how to make a test out of it. The current site (which has no redirects) has about 100k daily visits.

Best Answer

The effect of the 301 would be that the search engines will index /option-a instead of /option-x. Which is probably a good thing since /option-x is not reachable for the search index and thus could have a positive effect on the index. Only if you use this wisely ;-)

After the redirect put exit(); to stop the rest of the script to execute

header("HTTP/1.1 301 Moved Permanently"); 
header("Location: /option-a"); 
exit();

1. Basic answer

You can use the header() function to send a new HTTP header, but this must be sent to the browser before any HTML or text (so before the <!DOCTYPE ...> declaration, for example).

header('Location: '.$newURL);

2. Important details

die() or exit()

header("Location: http://example.com/myOtherPage.php");
die();

Why you should use die() or exit(): The Daily WTF

Absolute or relative URL

Since June 2014 both absolute and relative URLs can be used. See RFC 7231 which had replaced the old RFC 2616, where only absolute URLs were allowed.

Status Codes

PHP's "Location"-header still uses the HTTP 302-redirect code, this is a "temporary" redirect and may not be the one you should use. You should consider either 301 (permanent redirect) or 303 (other).

Note: W3C mentions that the 303-header is incompatible with "many pre-HTTP/1.1 user agents. Currently used browsers are all HTTP/1.1 user agents. This is not true for many other user agents like spiders and robots.

3. Documentation

HTTP Headers and the header() function in PHP

4. Alternatives

You may use the alternative method of http_redirect($url); which needs the PECL package pecl to be installed.

5. Helper Functions

This function doesn't incorporate the 303 status code:

function Redirect($url, $permanent = false)
{
    header('Location: ' . $url, true, $permanent ? 301 : 302);

    exit();
}

Redirect('http://example.com/', false);

This is more flexible:

function redirect($url, $statusCode = 303)
{
   header('Location: ' . $url, true, $statusCode);
   die();
}

6. Workaround

As mentioned header() redirects only work before anything is written out. They usually fail if invoked inmidst HTML output. Then you might use a HTML header workaround (not very professional!) like:

 <meta http-equiv="refresh" content="0;url=finalpage.html">

Or a JavaScript redirect even.

window.location.replace("http://example.com/");

Bash – In the shell, what does ” 2>&1 ” mean

File descriptor 1 is the standard output (stdout).
File descriptor 2 is the standard error (stderr).

Here is one way to remember this construct (although it is not entirely accurate): at first, 2>1 may look like a good way to redirect stderr to stdout. However, it will actually be interpreted as "redirect stderr to a file named 1". & indicates that what follows and precedes is a file descriptor and not a filename. So the construct becomes: 2>&1.

Consider >& as redirect merger operator.