PHP cURL error: "Empty reply from server" - php

Question

I have a class function to interface with the RESTful API for Last.FM - its purpose is to grab the most recent tracks for my user. Here it is:
private static $base_url = 'http://ws.audioscrobbler.com/2.0/';
public static function getTopTracks($options = array())
{
$options = array_merge(array(
'user' => 'bachya',
'period' => NULL,
'api_key' => 'xxxxx...', // obfuscated, obviously
), $options);
$options['method'] = 'user.getTopTracks';
// Initialize cURL request and set parameters
$ch = curl_init();
curl_setopt_array($ch, array(
CURLOPT_URL => self::$base_url,
CURLOPT_POST => TRUE,
CURLOPT_POSTFIELDS => $options,
CURLOPT_RETURNTRANSFER => TRUE,
CURLOPT_TIMEOUT => 30,
CURLOPT_USERAGENT => 'Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)'
));
$results = curl_exec($ch);
return $results;
}
This returns "Empty reply from server". I know that some have suggested that this error comes from some fault in network infrastructure; I do not believe this to be true in my case. If I run a cURL request through the command line, I get my data; the Last.FM service is up and accessible.
Before I go to those folks and see if anything has changed, I wanted to check with you fine folks and see if there's some issue in my code that would be causing this.
Thanks!
ANSWER: #Jan Kuboschek helped me stumble onto what is (maybe) going on here. By giving CURLOPT_POSTFIELDS an associative array, a particular content-type is specified that may not work with certain RESTful services. A smarter solution is to manually create a URL-encoded version of that data and pass that as the CURLOPT_POSTFIELDS.
For more info, check out: http://www.brandonchecketts.com/archives/array-versus-string-in-curlopt_postfields

Answer 1

A common issue are spaces in the URL - beginning, in the middle, or trailing. Did you check that out?
Edit - per comments below, spacing is not the issue.
I ran your code and had the same problem - no output whatsoever. I tried the URL and with a GET request, the server talks to me. I would do the following:
Use the following as $base_url: $base_url = 'http://ws.audioscrobbler.com/2.0/?user=bachya&period=&api_key=xxx&method=user.getTopTracks';
Remove the post fields from your request.
Edit
I moved your code out of the class since I didn't have the rest and modified it. The following code runs perfect for me. If these changes don't work for you, I suggest that your error is in a different function.
<?php
function getTopTracks()
{
$base_url = 'http://ws.audioscrobbler.com/2.0/?user=bachya&period=&api_key=8066d2ebfbf1e1a8d1c32c84cf65c91c&method=user.getTopTracks';
$options = array_merge(array(
'user' => 'bachya',
'period' => NULL,
'api_key' => 'xxxxx...', // obfuscated, obviously
));
$options['method'] = 'user.getTopTracks';
// Initialize cURL request and set parameters
$ch = curl_init($base_url);
curl_setopt_array($ch, array(
CURLOPT_URL => $base_url,
CURLOPT_RETURNTRANSFER => TRUE,
CURLOPT_TIMEOUT => 30,
CURLOPT_USERAGENT => 'Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)'
));
$results = curl_exec($ch);
return $results;
}
echo getTopTracks();
?>

Answer 2

The server received your request, but sent an empty response. Check the result of curl_getinfo($ch, CURLINFO_HTTP_CODE) to find out if the server responded with an HTTP error code.
Update: Ok so the server responds with the 100 Continue HTTP status code. In that case, this should solve your problem:
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Expect:'));
I found this here: PHP and cURL: Disabling 100-continue header. Hope it works!

Answer 3

I came acorss the same issue. My Http_code returned 200 but my response was empty. There could be many reasons for this as i experienced.
--Your hedaers might be incorrect
CURLOPT_HTTPHEADER => array('Content-Type:application/json', 'Expect:')
--You might need to send data as post fields in culr and not attached to the URl like url?p1=a1&p2=a2
$data = array (p1=>a1, p2=>a2)
CURLOPT_POSTFIELDS => $data
So your options array would be similar to the below
array(
CURLOPT_URL => $url,
CURLOPT_FAILONERROR => TRUE, // FALSE if in debug mode
CURLOPT_RETURNTRANSFER => TRUE,
CURLOPT_TIMEOUT => 4,
CURLOPT_HTTPHEADER => array('Content-Type:application/json', 'Expect:'),
CURLOPT_POST => TRUE,
CURLOPT_POSTFIELDS => $data,
);

Answer 4

According to Last.FM API documentation you should use GET method instead of POST to pass parameters. When I've changed POST to GET I've received the answer about incorrect key.

Answer 5

And here's the code for get Album Info from Laft.FM even if return error:
The Function:
function getAlbum($xml,$artist,$album)
{
$base_url = $xml;
$options = array_merge(array(
'user' => 'YOUR_USERNAME',
'artist'=>$artist,
'album'=>$album,
'period' => NULL,
'api_key' => 'xYxOxUxRxxAxPxIxxKxExYxx',
));
$options['method'] = 'album.getinfo';
// Initialize cURL request and set parameters
$ch = curl_init($base_url);
curl_setopt_array($ch, array(
CURLOPT_URL => 'http://ws.audioscrobbler.com/2.0/',
CURLOPT_POST => TRUE,
CURLOPT_POSTFIELDS => $options,
CURLOPT_RETURNTRANSFER => TRUE,
CURLOPT_TIMEOUT => 30,
CURLOPT_HTTPHEADER => array( 'Expect:' ) ,
CURLOPT_USERAGENT => 'Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)'
));
$results = curl_exec($ch);
unset ($options);
return $results;
}
Usage:
// Get the XML
$xml_error = getAlbum($xml,$artist,$album);
// Show XML error
if (preg_match("/error/i", $xml_error)) {
echo " <strong>ERRO:</strong> ".trim(strip_tags($xml_error));
}