Cron job to update Cloudflare's DNS to point to your current IP address. Useful for people with dynamic public IPs because their stupid ISP won't let them have a static one.

cron.php

<?php

    // Grab the IP address
    // This is the fastest method I've found so far
	$ip = system('dig +short myip.opendns.com @resolver1.opendns.com');

    // For cron logs 
	print "New IP is: " . $ip;
	
	$ch = curl_init();
	
	curl_setopt($ch, CURLOPT_URL, "https://www.cloudflare.com/api_json.html");
	curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
	curl_setopt($ch, CURLOPT_POST, true);

	$data = array(
		'a' => 'DIUP',
		'tkn' => 'put an api token in here please',
		'email' => 'also an email in here',
		'ip' => $ip,
		'hosts' => 'comma seperated domains pls'
	);

	curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
	echo $output = curl_exec($ch);
	$info = curl_getinfo($ch);
	curl_close($ch);

?>

So 8 years later, I (superNewb) and trying to achieve this same thing. I am guessing (hoping) that in 8 years, it may be a little easier to achieve? Like call using personal API, or something?

E.g. on my googleDomains DNS, I could just add the following cron job to my DDWRT router, and it'd run every 15 mins to check for an IP update. I am hoping there is something as - if not more - simple for cloudflare now?

0,15,30,45 * * * * root /usr/bin/curl -4 --user-agent curl -s -get https://MY_USER:MY_PASS@domains.google.com/nic/update?hostname=MY_DNS | /usr/bin/logger -s -t dns-updater

NB: GoogleDomains don't give API, so they generate random user/pass credentials for your DNS (i.e. 'MY_USER_MY_PASS' above.