PHP 8: Fix major compatibility issues

PHP8 deprecated, that class member variables can be created outside the class
definition or constructor, which prevented the code to run at all. Additionally
the error handling has changed, which has lead to multiple other errors during
the runtime.
Finally, strftime was deprecated in PHP 8.1.

index.php

@@ -87,7 +87,7 @@
 		'conference' => new GenericConference(),
 	));
 
-	if(startswith('//', @$GLOBALS['CONFIG']['BASEURL']))
+	if(isset($GLOBALS['CONFIG']['BASEURL']) && startswith('//', @$GLOBALS['CONFIG']['BASEURL']))
 	{
 		$tpl->set(array(
 			'httpsurl' => forceslash(forceslash('https:'.$GLOBALS['CONFIG']['BASEURL']).@$GLOBALS['MANDATOR']).forceslash($route).url_params(),
@@ -128,7 +128,7 @@
 		exit;
 	}
 
-	@list($mandator, $route) = explode('/', $route, 2);
+	list($mandator, $route) = array_pad(explode('/', $route, 2), 2, "");
 	if(!$mandator)
 	{
 		// root requested

lib/PhpTemplate.php

@@ -13,10 +13,12 @@ function h($s)
 class PhpTemplate
 {
 	private $data = array();
+	public $file;
 
 	public function __construct($file)
 	{
 		$this->file = $file;
+		$this->data["naked"] = false;
 	}
 
 	public function set($___data = array())

lib/helper.php

@@ -36,6 +36,9 @@ function joinpath($parts)
 
 function forceslash($url)
 {
+	if ($url == NULL) {
+		$url = "";
+	}
 	$url =  rtrim($url, '/');
 	if(strlen($url) > 0)
 		$url .= '/';