Show message if header location redirect fails

Question

I need to redirect to an unknown address. If the address is not available I would like to show a message to the user. How to do that?

<?php
header("Location: http://www.example.com/"); 
exit;
?>

Test the website first with `file_get_contents`. Then show an error if your website can't connect. — Dave Chen, May 09 '13 at 13:49
In the same spirit as @Dave but with probably better performance http://stackoverflow.com/questions/9841635/how-to-ping-a-server-with-php — Mihai Stancu, May 09 '13 at 13:50
Where is the address coming from? `get`? If so, have you considered possible problems with that. I.e. me redirecting users to `http://virusinfestedsite.com`? — PeeHaa, May 09 '13 at 13:50
@DaveChen's solution isn't perfect, but the only you can get. Once the browser followed the redirect to somewhere off-site, you have no control any more. — Lukas, May 09 '13 at 13:50
see http://stackoverflow.com/questions/2280394/check-if-an-url-exists-in-php — worenga, May 09 '13 at 13:53
I believe what is happening here is that you have a dynamic URL to which you require to redirect ONLY if the URL exists - else you have to give an error message. You can use cURL or what @Blazemonger suggested for this. cURL helps to know if the resource is available by checking the header of the response. You can [find an example here](http://stackoverflow.com/questions/1722613/check-if-a-remote-page-exists-using-php) Btw, that kind of makes this a duplicate question :) — raidenace, May 09 '13 at 13:53

score 2 · Accepted Answer · edited May 23 '17 at 10:25

2

The most direct method is to just retrieve the page:

if (file_get_contents('http://www.example.com/') !== false) {
  header("Location: http://www.example.com/"); 
  exit;
}

http://php.net/manual/en/function.file-get-contents.php

However, this only tells you if SOMETHING is available at that page. It won't tell you if, for instance, you got a 404 error page instead.

For that (and to save the memory cost of downloading the whole page), you can just get_headers() for the URL instead:

$url = "http://www.example.com/";
$headers = get_headers($url);
if (strpos($headers[0],'200 OK') !== false) { // or something like that
  header("Location: ".$url); 
  exit;
}

edited May 23 '17 at 10:25

Community

1
1

answered May 09 '13 at 13:50

Blazemonger

90,923
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The OP will need to do additional checks on the page itself. In any case, control is lost from there on. – Dave Chen May 09 '13 at 13:53
file_get_contents downloads the whole page, for the sake of availbility /memory this is a little much. – worenga May 09 '13 at 13:55
2

`get_headers()` might just be enough here. – Ja͢ck May 09 '13 at 13:57
@Jack So noted, editing. – Blazemonger May 09 '13 at 14:03
does `get_headers()` ignore the body content, in other words, does it save bandwidth on both sides? – Dave Chen May 09 '13 at 15:56
It should, yes. However, either way, if the URL doesn't work, you have to suffer through a delay until it times out. I don't think there's any way around that. – Blazemonger May 09 '13 at 16:00

score 0 · Answer 2 · answered May 09 '13 at 13:53

0

You can check if url exist then redirect:

$url = 'http://www.asdasdasdasd.cs';
//$url = 'http://www.google.com';

if(@file_get_contents($url))
{
    header("Location: $url"); 
}
else
{
    echo '404 - not found';
}

answered May 09 '13 at 13:53

Siamak Motlagh

5,028
7
41
65

score 0 · Answer 3 · answered May 09 '13 at 13:59

You can do it using curl

      $ch = curl_init(); 
      curl_setopt($ch, CURLOPT_URL, "http://www.example.com/"); 
      $output = curl_exec($ch); 
      if(curl_errno($ch)==6)
        echo "page not found";
     else
      header("Location: http://www.example.com/");      

       curl_close($ch);

Show message if header location redirect fails

3 Answers3