I would like to set up a cron job which sends an http request to a url. How would I do this? I have never set up a cronjob before.
A cron job is just a task that get's executed in the background at regular pre-set intervals.
You can pretty much write the actual code for the job in any language - it could even be a simple php script or a bash script.
PHP Example:
#!/usr/bin/php -q
Next, schedule the cron job:
10 * * * * /usr/bin/php /path/to/my/php/file > /dev/null 2>&1
... the above script will run every 10 minutes in the background.
Here's a good crontab tutorial: http://net.tutsplus.com/tutorials/other/scheduling-tasks-with-cron-jobs/
You can also use cURL to do this depending on what request method you want to use:
$url = 'http://www.example.com/submit.php';
// The submitted form data, encoded as query-string-style
// name-value pairs
$body = 'monkey=uncle&rhino=aunt';
$c = curl_init ($url);
curl_setopt ($c, CURLOPT_POST, true);
curl_setopt ($c, CURLOPT_POSTFIELDS, $body);
curl_setopt ($c, CURLOPT_RETURNTRANSFER, true);
$page = curl_exec ($c);
curl_close ($c);