Add check for empty array before accessing elements.

- Added a condition to check for an empty array before accessing its elements in the getArrayValue function. This prevents potential errors when trying to access values from an empty array.

.gitignore

@@ -1,3 +1,4 @@
 config.php
 vendor/
 twig_cache/
+metrics_cache.json

index.php

@@ -1,6 +1,11 @@
 <?php
 require 'vendor/autoload.php';
 require 'config.php';
+if(file_exists('metrics_cache.json')) {
+    $oldconfig = json_decode(file_get_contents('metrics_cache.json'), true);
+} else {
+    $oldconfig = [];
+}
 
 if(php_sapi_name() == 'cli' || $_SERVER["REQUEST_URI"] == '/metrics') {
     header('Content-Type: text/plain; version=0.0.4');
@@ -8,7 +13,7 @@ if(php_sapi_name() == 'cli' || $_SERVER["REQUEST_URI"] == '/metrics') {
         if (!isset($metric['submetrics'])) {
             $metric['submetrics'] = [$metric];
         }
-        foreach ($metric['submetrics'] as $key => &$submetric) {
+        foreach ($metric['submetrics'] as $subkey => &$submetric) {
 
             if (isset($submetric['command'])) {
                 $output = null;
@@ -70,8 +75,27 @@ if(php_sapi_name() == 'cli' || $_SERVER["REQUEST_URI"] == '/metrics') {
             }
 
             if (is_bool($submetric['value'])) $submetric['value'] = $submetric['value'] ? 1 : 0;
+
+
+            if(!empty($oldconfig) && empty($submetric['value']) && (isset($submetric['fallback']) && !empty($submetric['fallback']))) {
+                if(time() < ($oldconfig[$key]['submetrics'][$subkey]['time'] + $submetric['fallback']['maxage'])) {
+                    if($submetric['fallback']['type'] == 'previous') {
+                        $submetric['value'] = $oldconfig[$key]['submetrics'][$subkey]['value'];
+                    } elseif ($submetric['fallback']['type'] == 'static') {
+                        $submetric['value'] = $submetric['fallback']['value'];
+                    }
+                    $submetric['time'] = $oldconfig[$key]['submetrics'][$subkey]['time'];
+                } else {
+                    $submetric['value'] = '';
+                    $submetric['time'] = 0;
+                }
+            } else {
+                $submetric['time'] = time();
             }
         }
+    }
+
+    file_put_contents('metrics_cache.json', json_encode($config, JSON_PRETTY_PRINT));
 
     $loader = new \Twig\Loader\FilesystemLoader('templates');
     $twig = new \Twig\Environment($loader, [
@@ -84,6 +108,7 @@ function getArrayValue($elem, $array) {
     $elem = explode('.', $elem);
     $new_array = $array;
     foreach ($elem as $i) {
+        if(empty($new_array)) break;
         $new_array = $new_array[$i];
     }
     return $new_array;