refactor: translate comments, add TODOs for future dynamic data loading

Enhances code clarity by translating German comments to English and adding comments and TODOs for dynamic data loading
and generation of currencies, API data, language files, and HTML elements.
This will reduce hardcoded values and improve maintainability. Also, adds a
reminder to move scripts to separate files and add OpenGraph tags in the HTML.

No breaking changes, but dynamically loading these values will be essential
for improving the codebase in future iterations.

index.php

@@ -4,6 +4,8 @@ header("Cache-Control: no-store, no-cache, must-revalidate, max-age=0");
 header("Cache-Control: post-check=0, pre-check=0", false);
 header("Pragma: no-cache");
 
+// Array of supported currencies
+// TODO: Load dynamically from the API data
 $array = array("EUR",
 	"USD",
 	"GBP",
@@ -57,14 +59,16 @@ $array = array("EUR",
 
 include('coingecko.php');
 
-// Holt die API Daten
+// Fetches the API data from the JSON file
+// TODO: This doesn't exist on first load, so it will display warnings
 $api_cg = json_decode(file_get_contents('coingecko.json'));
 
-// Holt die Zeit der letzten Abfrage
+// Fetches the time of the last API data update
 $time_cg = date("H:i:s", $api_cg->time);
 $time = $time_cg;
 
-// Holt die einzelnen Werte für die Berechnung
+// Fetches the individual currency values from the API data
+// TODO: Make that dynamic
 $BTC = $api_cg->btc->lastValue;
 $EUR = $api_cg->eur->lastValue;
 $USD = $api_cg->usd->lastValue;
@@ -116,7 +120,7 @@ $CZK = $api_cg->czk->lastValue;
 $DKK = $api_cg->dkk->lastValue;
 $MXN = $api_cg->mxn->lastValue;
 
-// Lädt die Sprachdatei, nach der Sprache die im Browser eingestellt wurde
+// Load the language file based on the browser language
 if(array_key_exists('HTTP_ACCEPT_LANGUAGE', $_SERVER)){
     $lang = substr($_SERVER['HTTP_ACCEPT_LANGUAGE'], 0, 2);
 }else{
@@ -255,6 +259,8 @@ $xmr_in_fiat = strtr($xmr_in_fiat, ",", " ");
     <meta name="description" lang="<?php echo $lang_meta; ?>" content="<?php echo $meta_description; ?>"/>
     <meta name="keywords" lang="<?php echo $lang_meta; ?>" content="<?php echo $meta_keywords; ?>"/>
 
+    <!-- TODO: Add corresponding OpenGraph tags -->
+    
     <link rel="apple-touch-icon-precomposed" sizes="57x57" href="img/apple-touch-icon-57x57.png" />
     <link rel="apple-touch-icon-precomposed" sizes="114x114" href="img/apple-touch-icon-114x114.png" />
     <link rel="apple-touch-icon-precomposed" sizes="72x72" href="img/apple-touch-icon-72x72.png" />
@@ -306,6 +312,7 @@ $xmr_in_fiat = strtr($xmr_in_fiat, ",", " ");
                     <h1 lang="<?php echo $lang_meta; ?>"><span style="color:#4d4d4d;">&darr;</span>&nbsp;<span style="color:#ff6600;" title="Monero">XMR</span>&nbsp;<?php echo $title_h1;?>&nbsp;<span style="color:#4d4d4d;">&darr;</span></h1>
                     <div class="fiat-btns table-responsive">
                         <table class="table table-sm table-borderless">
+                            <!-- TODO: Generate this table dynamically -->
                             <tbody>
                                 <tr>
                                     <td><button type="button" class="btn btn-light" title="<a class='text-decoration-none fiat-tooltip' href='/'><b><?php echo $l_eur; ?></b></a>" data-toggle="tooltip" data-bs-html="true" data-placement="top">EUR</button></td>
@@ -457,6 +464,7 @@ $xmr_in_fiat = strtr($xmr_in_fiat, ",", " ");
                             echo '<option value="'.$xmr_in.'">'.$xmr_in.'</option>';
                         }
                         ?>
+                        <!-- TODO: Populate this select box dynamically -->
                         <option value="EUR" label="<?php echo $l_eur; ?>">EUR</option>
                         <option value="USD" label="<?php echo $l_usd; ?>">USD</option>
                         <option value="GBP" label="<?php echo $l_gbp; ?>">GBP</option>
@@ -524,6 +532,7 @@ $xmr_in_fiat = strtr($xmr_in_fiat, ",", " ");
     </div>
 
 
+<!-- TODO: Move these scripts to a separate file -->
 <script type="text/javascript">
     function fiatConvert(value)
     {
@@ -531,6 +540,7 @@ $xmr_in_fiat = strtr($xmr_in_fiat, ",", " ");
         let xmrValue = document.getElementById("xmrInput");
         let selectBox = document.getElementById("selectBox").value;
 
+        // TODO: Do this dynamically
         if (selectBox == "BTC") {
                 let value = fiatAmount / <?php echo $BTC; ?>;
                 xmrValue.value = value.toFixed(12);
@@ -692,6 +702,8 @@ $xmr_in_fiat = strtr($xmr_in_fiat, ",", " ");
         let fiatValue = document.getElementById("fiatInput");
         let selectBox = document.getElementById("selectBox").value;
 
+        // TODO: Do this dynamically
+
         if (selectBox == "BTC") {
                 let value = xmrAmount * <?php echo $BTC; ?>;
                 fiatValue.value = value.toFixed(8);