I’ve been doing a lot of work with services and working with them in various ways from PHP. There are a few different ways to do this, PHP has a curl extension which is useful, and if you can add PECL extensions then pecl_http is a better bet but there are a couple of different ways of using it. This post shows all these side-by-side.

POSTing from PHP Curl

This is pretty straightforward once you get your head around the way the PHP curl extension works, combining various flags with setopt() calls. In this example I’ve got a variable $xml which holds the XML I have prepared to send – I’m going to post the contents of that to flickr’s test method.

$url = 'http://api.flickr.com/services/xmlrpc/';
$ch = curl_init($url);

curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $xml);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);

$response = curl_exec($ch);
curl_close($ch);

First we initialised the connection, then we set some options using setopt(). These tell PHP that we are making a post request, and that we are sending some data with it, supplying the data. The CURLOPT_RETURNTRANSFER flag tells curl to give us the output as the return value of curl_exec rather than outputting it. Then we make the call and close the connection – the result is in $response.

POSTing from Pecl_Http

Pecl_Http has two interfaces – one procedural and one object-oriented; we’ll start by looking at the former. This is even simpler than in curl, here’s the same script translated for pecl_http:

$url = 'http://api.flickr.com/services/xmlrpc/';

$response = http_post_data($url, $xml);

This extension has a method to expressly post a request, and it can optionally accept data to go with it, very simple and easy.

POSTing from Pecl_Http: the OO interface

Finally let’s see what the OO verison of the extension looks like. Exactly the same call as both the above examples, but using the alternative interface, means our code looks like this:

$url = 'http://api.flickr.com/services/xmlrpc/';

$request = new HTTPRequest($url, HTTP_METH_POST);
$request->setRawPostData($xml);
$request->send();
$response = $request->getResponseBody();

This example is quite a bit longer than the previous one, and you might think this indicates that this approach is more complicated. In some senses that is true and its probably overkill for our extremely trivial example. However it is worth mentioning that the pecl_http extension is extremely flexible and powerful, and can handle some cases that the curl extension can’t. So even if it looks more complicated here, it can still be an excellent choice to implement.

In Conclusion

That was a very fast round-up of three ways you could make an arbitrary web service call from PHP – hopefully these examples are clear and will help anyone just starting to implement something along these lines.