Trapping file_get_contents for bad urls

[Csaba Gabor]

I've got a section of code that takes a user supplied $url and
essentially does:
function redirectRequest($url) {
$resultRemote = @file_get_contents($url);
return $resultRemote; }

Is there a reasonable way to trap for and differentiate between the
major (most common) types of failure?

For example, common scenarios in which I would not get back a desired
response include: malformed url, the domain can't be mapped (ie. the
DNS servers don't return an IP address), the domain is not reachable,
the directory or file is not found, standard HTTP error response
header.
I'm sure it's been solved many times over, but my searches didn't lead
me to substantive results. My initial attempt only captures the fact
that there was a problem, but not the nature of it:

function redirectRequest($url) {
$oldTrack = ini_set("track_errors","true"); // allow $php_errormsg
to be set
$php_errormsg = ""; // initialize; will be set
if error with next line
$resultRemote = @file_get_contents($url);
ini_set("track_errors",$oldTrack); // restore setting
if ($php_errormsg) return -1; // this site had a problem
return $resultRemote; }
Thanks for any pointers,
Csaba Gabor from Vienna

Note: This is to be used between cooperating domains where each server
puts out a serialized response when it receives a redirectRequest as
above. So if the requesting site can't unserialize the return value,
it knows there is a problem, but this would still leave a user (which
for now is me) confused as to the source of the problem.

[Chung Leong]

In theory, you can create a stream context, then attach a callback
function to it to receive notifications:

$context = stream_context_create(array());
stream_context_set_params($context, array('notification' =>
'stream_callback'));
$f = fopen("http://www.google.com/", "rb", false, $context);

The parameters passed to the function are as followed:

function stream_callback(
$notifycode,
$severity,
$xmsg,
$xcode,
$bytes_sofar,
$bytes_max)

Notification codes are defined as such:

1 = RESOLVE
2 = CONNECT
3 = AUTH_REQUIRED
4 = MIME_TYPE_IS
5 = FILE_SIZE_IS
6 = REDIRECTED
7 = PROGRESS
8 = COMPLETED
9 = FAILURE
10 = AUTH_RESULT

Severity codes:

0 = INFO
1 = WARNING
2 = ERROR

In practice, however, the PHP stream API is somewhat of a
work-in-progress. Not everything is listed above is actually
implemented. As of PHP 4.3.6, the callback doesn't receive
notifications for the resolve stage.

[Mara Guida]

Csaba Gabor wrote:

I've got a section of code that takes a user supplied $url and
essentially does:
function redirectRequest($url) {
$resultRemote = @file_get_contents($url);
return $resultRemote; }

<snip>
Try cURL
http://www.php.net/curl

[NC]

Csaba Gabor wrote:

I've got a section of code that takes a user supplied $url and
essentially does:
function redirectRequest($url) {
$resultRemote = @file_get_contents($url);
return $resultRemote; }

Is there a reasonable way to trap for and differentiate between
the major (most common) types of failure?
Not if you insist on using file_get_contents()...
For example, common scenarios in which I would not get back a desired
response include: malformed url, the domain can't be mapped (ie. the
DNS servers don't return an IP address), the domain is not reachable,
the directory or file is not found, standard HTTP error response
header.

Consider an alternative function that does something like this:

1. Parse the argument URL into parts using parse_url() to
verify that it is not obvously malformed.
2. Run the server name through gethostbyname() to verify
that the host name in fact resolves to an IP address.
3. Connect to the server using fsockopen() to verify that
it is operational.
4. Attempt to retrieve the file by emulating a GET request
with fputs() and reading response by fgets().
5. Parse the response headers and, if applicable, the body.

Cheers,
NC