checking if file on another website has changed? (have starter curl example)

[ultrus]

Hello,

I'm using curl to grab a new solar image once an hour or so from the Solar Dynamics Observatory (example below). I'm trying to archive new images and am struggling with that.

 

If I download an image, the filetime() function returns the current time since I downloaded it and wrote it to a fresh file. The result is that the file is always "new", even if the image hasn't changed on the SDO website. Do you have an idea on how to check the last modified time of a file through curl or other means so that I'm not downloading duplicate images?

 

Thanks a ton!

 

 

//fetch image
$ch = curl_init("http://www.somewebsite.com/theimage.jpg");
curl_setopt($ch,CURLOPT_FOLLOWLOCATION,1);
$file = "../images/latest/theimage.jpg";
$fp = fopen($file, "w");
curl_setopt($ch, CURLOPT_FILE, $fp);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_exec($ch);
curl_close($ch);
fclose($fp);

//this part is no good...
//get last modified date
if (file_exists($file)) {
$filetime = filemtime($file);
}

[trq]

Do you have an idea on how to check the last modified time of a file through curl

 

The file system on the server is responsible for such information. Its not normally made available to requesting clients.

[ultrus]

I'm digging, so far I might be able to get the Last-Modified header of a remote file using curl:

http://stackoverflow.com/questions/845220/get-the-last-modified-date-of-a-remote-file

 

Not working yet as I'm using it within a class. I'll post if I get it working. Any thoughts?

[trq]

That will be all that is available. Not real reliable but It's likely your best option.

[ultrus]

SOLVED

Source: http://stackoverflow.com/questions/845220/get-the-last-modified-date-of-a-remote-file

 

$curl = curl_init("http://www.somewebsite.com/theimage.jpg");
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl, CURLOPT_NOBODY, true);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl, CURLOPT_FILETIME, true);
$result = curl_exec($curl);

if ($result === false) {
die (curl_error($curl)); 
}

$timestamp = curl_getinfo($curl, CURLINFO_FILETIME);
if ($timestamp != -1) { //otherwise unknown
echo date("Y-m-d H:i:s", $timestamp); //etc
}