Check (every 15 seconds) if a website is updated

henkealf

I need some php-code that, every 15 seconds, will check if a website is updated in any way.
I could have a browser window open with the code running, so no cron-job or such is needed.

Thanks!

henkealf

Could something like this do the job?

<?php

echo "<html>";
echo "<head>";
echo "<meta http-equiv="refresh\" content=\"15\">";
echo "</head>";

$filename = "http://www.thesite.com/page.html";
$handle = fopen($filename, "r");
$contents = fread($handle, filesize($filename));

$filenamebackup = "http://www.mybackupofthesite.com/page.html";
$handlebackup = fopen($filenamebackup, "r");
$contentsbackup = fread($handle, filesize($filename));

if($contents!=$contentsbackup) echo "The website has been updated!"

fclose($handle);

Weedpacket

If you use the socket functions you could send an "If-Modified-Since:" header with the time and date of the previous check (fifteen seconds ago). Then (assuming the server looks at the header) you'll get back a 304 Not Modified response if there has been no change, or a 200 response if there has (or if the server doesn't look at the header).

If you know the server respects the If-Modified-Since header, then you can use a HEAD request instead of a GET, and save yourself the work of retrieving the entire page.

Oh, and PS: filesize() doesn't work on resources retrieved via http URLs in versions of PHP<5.

henkealf

Originally posted by Weedpacket
If you use the socket functions you could send an "If-Modified-Since:" header with the time and date of the previous check (fifteen seconds ago). Then (assuming the server looks at the header) you'll get back a 304 Not Modified response if there has been no change, or a 200 response if there has (or if the server doesn't look at the header).

Thanks, but could you or someone else please show me an example of what a usefil code snippet would look like.

Installer

If "if-modified-since" doesn't work (it often won't) and you have PHP5 then try filemtime() or stat(). Otherwise, this should work:

$compare_file = 'compare.txt';
$url = 'http://www.example.com/page.html';
$url_return = file_get_contents($url);
/**
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$url_return = curl_exec($ch);
curl_close($ch);
**/
if (file_exists($compare_file)) {
    $compare_str = file_get_contents($compare_file);
    if ($compare_str == $url_return) {
        echo 'File has not changed.<br />';
    } else {
        echo 'File has changed.<br />';
        write_compare_file($compare_file, $url_return);
    }
} else {
    echo 'No storage file to compare; ' .
         $compare_file . ' being written.<br />';
    write_compare_file($compare_file, $url_return);
}

function write_compare_file($file, $str)
{
    $fp = fopen($file, 'w');
    fwrite($fp, $str);
    fclose($fp);
    return true;
}

If that doesn't work then you probably don't have fopen wrappers enabled. In that case, if you have curl enabled, delete the first "file_get_contents()" line and the comment markers. If you don't have either fopen wrappers or curl enabled you'll have to do something else.

henkealf

Neither filemtime nor stat works with external pages, why not?
The code below works fine with files in the same directory.

<?php

$filename = 'http://www.thesite.com/index.php';
echo "$filename was last modified: " . date ("F d Y H:i:s.", filemtime($filename));

echo "<BR><BR>";

$statvar = stat('$filename');
echo date("F d Y H:i:s.",$statvar[9]);

Installer

My mistake; "stat()" (and "filemtime()" since it uses "stat()") will work remotely only with the ftp protocol, and only with v>=5.

sfullman

add this code at the bottom:

Now, check.php would just have a redirect timeout (using javascript) which would refresh itself every 15 seconds. If the page is the same, just output a javascript to set another timeout. If however the page has changed, you can do several things:

window.parent.location=window.parent.location+""
you can use the innerHTML property to just refresh content in the parent page which has changed - so for example youhave a div in the parent called <div id="content">old stuff here</div>

just print the same div in teh iframe page, and after the div, using js, say:

window.parent.document.getElementById('content').innerHTML=document.getElementById('content').innerHTML;

you can alert the user that new content is available in a status bar so they don't rudely have the rug pulled out under them.

Sam