PHP script to update dynamic IP on afraid's freedns service. Works on PHP 7.0

fdupdate.php

<?php
/*************************************************************************/
/* Copyright (c) 2020 by Alfonso Vivancos                                */
/* Based on the work by Giovanni Derks (http://derks.me.uk/)             */
/* https://vivancos.eu                                                   */
/*                                                                       */
/* This program is free software. You can redistribute it and/or modify  */
/* it under the terms of the GNU General Public License as published by  */
/* the Free Software Foundation; either version 2 of the License.        */
/*************************************************************************/

$using_router=1;
$get_ip_from_url="http://ifconfig.co/ip";


$code[]="YOUR-STRING-HERE";


// --------------------------------------------------------------------------

echo("------------------------------------------------------------\n");
echo("FreeDNS update scritp\n");
echo("------------------------------------------------------------\n");
echo("Developed by Giovanni Derks\n");
echo("Modified by Alfonso Vivancos\n");
echo("Released under the terms of the GNU General Public License.\n");
echo("------------------------------------------------------------\n\n");

$done=0;
$rcnt=0;

while((!$done) && ($rcnt < 15)) {

	echo("Finding your IP...                                 ");

	if (!$using_router) {
		$ip=$_SERVER["REMOTE_ADDR"];
	}
	else {
		$ip=@file_get_contents($get_ip_from_url);
	}

	if ($ip != "")
		echo("   [ OK ]");
	else
		echo("[ Error ]");


	echo("\n\nYour ip is: ".$ip."\n\n");
	if (file_exists("last_ip.txt"))
		$last_ip=trim(file_get_contents("last_ip.txt"));
	else
		$last_ip="";

	if (($last_ip != $ip) && ($ip != "")) {

		foreach($code as $key=>$val) {
			exec("wget \"http://freedns.afraid.org/dynamic/update.php?".$val."\" -O update.php -q");
			echo(file_get_contents("update.php"));
			exec("rm update.php");
			echo("\n\n");
		}

		save_file("last_ip.txt", $ip);
		if (file_exists("log.txt"))
			$log=file_get_contents("log.txt");
		else
			$log="";

		$lines=explode("\n", $log);

		$log=date("Y-m-d H:i:s")." - Updated: ".$ip."\n";
		for($i=0; $i<count($lines); $i++) {
			if($lines[$i] != "") $log.=$lines[$i]."\n";
		}

		save_file("log.txt", $log);

	}


	if ($ip == "") {
		echo("Ip not found, will try again in 20 seconds...       [ ".($rcnt+1)."/15 ]\n\n");
		sleep(20);
	}
	else {

		echo("\n------------------------------------------------------------\n");
		echo("All done!");
		echo("\n------------------------------------------------------------\n\n");
		$done=1;

	}

	$rcnt++;
}

if (!$done) echo("Giving up...\n\n");



// -------------------------------------------------------------------------

function save_file($fn, $txt) {

	if ($handle=fopen($fn, 'w+')) {

		if (fwrite($handle, $txt) === FALSE) {
				echo "\n - Error: cannot write to file [ $fn ]\n";
				exit;
		}


		fclose($handle);
	}

}


?>