How can I securely send a url with GET info from a crontab php script to another server?

I have a client PHP script I'm writing that will execute via crontab. I need it to collect some info about the system (cpu, ram, hd, uptime, etc) and then send it to another server on the internet where I can log the info into a mysql database. I was thinking a url like so: http://checkin.mycompany.com/checkin.php?cpu=1000&ram=256&uptime=1.0,2.0,3.0 &.... My first question is, how do I actually do that the best way? Shall I use the header() or fopen() or fsockopen()? I was thinking I could also encrypt the whole string somehow so it would be like http://checkin.mycompany.com/checkin.php?info=ap34um5sfo85s5o8sop58sp84a84y5 8ay4nay984nyf0a9ny40 (Then just split it back out on the server end again based upon my algorithm.) Or is it better to simulate a form post (GET/POST) simulation somehow? And if so, how can I 'secure' that? My apache server has https:// enabled. The key here is that the 'clients' might be behind firewalls, and so it's most likely that port 80 will be open. Working examples (links/code) greatly appreciated.