Handle CURL headers before downloading body - php

Question

Using PHP and CURL (unless there is a better alternative then CURL in this case), is it possible to have a php function handle the header response before downloading the file?
For example:
I have a script that downloads and processes urls supplied by the user. I would like to add a check so that if the file is not valid for my process (not a text file, too large, etc),the CURL request would be cancelled before the server wastes time downloading the file.
Update: Solution
PEAR class HTTP_Request2: http://pear.php.net/package/HTTP_Request2/
Gives you the ability to set observers to the connection and throw exceptions to cancel anytime. Works perfectly for my needs!

Answer 1

Using cURL, do a HTTP HEAD request to check the headers, then if it is valid (the status is 200) do the full HTTP GET request.
The basic option you must set is CURLOPT_NOBODY, which changes the requested to the type HEAD
curl_setopt($ch, CURLOPT_NOBODY, true);
Then after executing the query, you need to check the return status which can be done using curl_getinfo()
$status = curl_getinfo($ch, CURLINFO_HTTP_CODE);

Answer 2

I know this is an old topic but just in case people comes here in the future.
With CURL, you can use CURLOPT_WRITEFUNCTION, who let's you place a callback that will be called as soon as the body response starts coming and needs to be written. In that moment you can read the headers and cancel the process and the body will not be downloaded. All in one request.
For a deeper look and code examples see PHP/Curl: inspecting response headers before downloading body

Answer 3

This is an example how you can solve it:
// Include the Auth string in the headers
// Together with the API version being used
$headers = array(
"Authorization: GoogleLogin auth=" . $auth,
"GData-Version: 3.0",
);
// Make the request
curl_setopt($curl, CURLOPT_URL, "http://docs.google.com/feeds/default/private/full");
curl_setopt($curl, CURLOPT_HTTPHEADER, $headers);
$response = curl_exec($curl);
curl_close($curl);
// Parse the response
$response = simplexml_load_string($response);
// Output data
foreach($response->entry as $file)
{
//now you can do what ever if file type is a txt
//if($file->title =="txt")
// do something
else
// do soething
echo "File: " . $file->title . "<br />";
echo "Type: " . $file->content["type"] . "<br />";
echo "Author: " . $file->author->name . "<br /><br />";
}