如何检查网站是否可访问？

Question

I want to see if a website can be accessed or not with a PHP page.

Here is my plan:

<?php 
  $website = /* bool to see if site is up */
  if($website)
{
  echo'<iframe src="http://64.126.89.241/" width="100%" height="100%"/>';  
}else
{
  echo'<iframe src="http://tsiserver.us/backup/" width="100%" height="100%"/>';  
}
?>

The website will be hosted on another server, therefore if my internet goes down, a user may access the backup version of a site.

Answer 1

Here is a simple function that will determine if a website exists using PHP and cURL

function urlExists($url=NULL)  
{  
    if($url == NULL) return false;  
    $ch = curl_init($url);  
    curl_setopt($ch, CURLOPT_TIMEOUT, 5);  
    curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 5);  
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);  
    $data = curl_exec($ch);  
    $httpcode = curl_getinfo($ch, CURLINFO_HTTP_CODE);  
    curl_close($ch);  
    if($httpcode>=200 && $httpcode<300){  
        return true;  
    } else {  
        return false;  
    }  
}  

This was grabbed from this post on how to check if a URL exists. Because Twitter should provide an error message above 300 when it is in maintenance, or a 404, this should work perfectly.

reference : https://stackoverflow.com/a/1239090/568414