diff --git a/homepage/participo/pmelo.inc.php b/homepage/participo/pmelo.inc.php
index 5cfaeb6..b6304a3 100644
--- a/homepage/participo/pmelo.inc.php
+++ b/homepage/participo/pmelo.inc.php
@@ -1,19 +1,20 @@
-<?php 
+<?php
 setlocale(LC_ALL, "de_DE@euro", "de_DE", "de", "ge");
 set_include_path(get_include_path() . PATH_SEPARATOR . "./lib/");
 
 // Configs
-require_once("config/participo.php");
-require_once $config['basePath'] . "/config/cwsvJudo.config.php";
+require_once "config/participo.php";
+require_once $config["basePath"] . "/config/cwsvJudo.config.php";
 
 // Libs
-require_once("participoLib/user.php");
+require_once "participoLib/user.php";
 
 participo::init($cwsvJudoConfig);
 
 $pmelo = new PmElo();
 
-class PmElo{
+class PmElo
+{
     function __construct()
     {
         // $this->var_log($_SESSION, "session");
@@ -21,106 +22,163 @@ class PmElo{
         session_start();
 
         // create 'pmelo' section in the sessions data
-        if(!array_key_exists('pmelo', $_SESSION)){
-            $_SESSION['pmelo'] = [];
-        }        
-        // - data storage for id-s of chosen fighters
-        if(!array_key_exists('fighterIds', $_SESSION['pmelo'])){
-            $_SESSION['pmelo']['fighterIds'] = []; 
+        if (!array_key_exists("pmelo", $_SESSION)) {
+            $_SESSION["pmelo"] = [];
         }
-
-        // check for action in post data
-        if(array_key_exists('pmelo', $_POST)){
-            if(array_key_exists('fighterIds', $_POST['pmelo'])){
-                $_SESSION['pmelo']['fighterIds']=$_POST['pmelo']['fighterIds'];
-            }
-            // $this->var_log($_SESSION, "session");
+        // - data storage for id-s of chosen fighters
+        if (!array_key_exists("fighterIds", $_SESSION["pmelo"])) {
+            $_SESSION["pmelo"]["fighterIds"] = [];
         }
 
         // load/recreate ranking data
-        if(!is_file(self::$pmeloJson)){
-            $this->log['info'][] = "Couldn't find `".self::$pmeloJson."`. Create a new one!";
+        if (!is_file(self::$pmeloJson)) {
+            $this->log["info"][] =
+                "Couldn't find `" . self::$pmeloJson . "`. Create a new one!";
             file_put_contents(self::$pmeloJson, json_encode([]));
         }
 
         // init members
         $this->trainees = self::getTrainees();
-        $this->var_log(array_map(function($user){return $user->getFirstName();},$this->trainees), "trainees from db");
+        $this->var_log(
+            array_map(function ($user) {
+                return $user->getFirstName();
+            }, $this->trainees),
+            "trainees from db"
+        );
         $this->rankings = $this->createRankings();
-        $this->var_log(array_map(function($id){return $this->trainees[$id]->getFirstName();},$this->rankings), "current ranking");
+        $this->var_log(
+            array_map(function ($id) {
+                return $this->trainees[$id]->getFirstName();
+            }, $this->rankings),
+            "current ranking"
+        );
         $this->fighters = [];
-        foreach($_SESSION['pmelo']['fighterIds'] as $id){
+        foreach ($_SESSION["pmelo"]["fighterIds"] as $id) {
             $this->fighters[$id] = $this->trainees[$id];
-        };
-        $this->var_log(array_map(function($user){return $user->getFirstName();},$this->fighters), "fighters");
-        
+        }
+        $this->var_log(
+            array_map(function ($user) {
+                return $user->getFirstName();
+            }, $this->fighters),
+            "fighters"
+        );
+
+        // @todo Can be split. Some actions need the members to be already filled, some could be done earlier.
+        // check for action in post data
+        if (array_key_exists("pmelo", $_POST)) {
+            // setting the current fighters
+            // - meaning: fighter list is automatically updated by posted fighters
+            if (array_key_exists("fighterIds", $_POST["pmelo"])) {
+                $_SESSION["pmelo"]["fighterIds"] =
+                    $_POST["pmelo"]["fighterIds"];
+
+                header("Location: .");
+            }
+
+            if (array_key_exist("promote", $_POST["pmelo"])) {
+                $promote = $_POST["pmelo"]["promote"];
+                $this->promote(
+                    $promote["promoteeId"],
+                    $promote["promoteeRank"],
+                    $promote["degradeeId"],
+                    $promote["degradeeRank"]
+                );
+
+                header("Location: .");
+            }
+
+            // $this->var_log($_SESSION, "session");
+        }
 
         // save the updated ranking
         // @todo should be in destructor
         self::saveRankings($this->rankings);
     }
 
-    function __destruct(){
+    function __destruct()
+    {
         // sad, the destructor is not allowed to use file_put_contents
     }
-    
+
     // load all active trainees into a id=>User assoc array
-    public static function getTrainees(){
-        $traineeList = array_map('User::fromDbArray', User::dbSelectWithAttribute(4));
+    public static function getTrainees()
+    {
+        $traineeList = array_map(
+            "User::fromDbArray",
+            User::dbSelectWithAttribute(4)
+        );
         $traineeAssocArray = [];
-        foreach($traineeList as $trainee){
+        foreach ($traineeList as $trainee) {
             $traineeAssocArray[$trainee->getId()] = $trainee;
         }
         return $traineeAssocArray;
     }
 
     // load ranking from json file
-    public static function loadRankings(){
+    public static function loadRankings()
+    {
         return json_decode(file_get_contents(self::$pmeloJson));
     }
-    
+
     // save a ranking to json file
-    public static function saveRankings(array $rankings){
+    public static function saveRankings(array $rankings)
+    {
         file_put_contents(self::$pmeloJson, json_encode($rankings));
     }
 
     // simple logger to a logging buffer
-    function var_log($variable, string $prefix=null, string $logChannel='info'){
-        if(!in_array($logChannel, ['info', 'warning', 'error'])){
-            $logChannel='info';
+    function var_log(
+        $variable,
+        string $prefix = null,
+        string $logChannel = "info"
+    ) {
+        if (!in_array($logChannel, ["info", "warning", "error"])) {
+            $logChannel = "info";
         }
-        $prefix = (!empty($prefix) ? $prefix.": " : "");
-        $this->log[$logChannel][]=$prefix.var_export($variable, true);
+        $prefix = !empty($prefix) ? $prefix . ": " : "";
+        $this->log[$logChannel][] = $prefix . var_export($variable, true);
     }
 
     // create the ranking for the current session (load saved ranking from file, remove old trainees, add new trainees)
-    public function createRankings(){
+    public function createRankings()
+    {
         // load the last state of the ranking
         $loadedRanking = self::loadRankings();
-        $this->var_log(array_map(function($id){$user=$this->trainees[$id]; return $user->getFirstName();}, $loadedRanking), "loaded ranking");
+        $this->var_log(
+            array_map(function ($id) {
+                $user = $this->trainees[$id];
+                return $user->getFirstName();
+            }, $loadedRanking),
+            "loaded ranking"
+        );
 
         // check if the ranked trainees still are in training
         // - the ranking with
         $cleanRanking = [];
         // - trainees that aren't currently in the ranking for later inserting
         $toBeInsertedTrainees = $this->trainees;
-        foreach($loadedRanking as $id){
-            if(array_key_exists($id, $this->trainees)){
+        foreach ($loadedRanking as $id) {
+            if (array_key_exists($id, $this->trainees)) {
                 // userId is still in training, so append it to the cleaned up ranking
                 $cleanRanking[] = $id;
                 // trainees already in the ranking we won't have to insert manual
                 unset($toBeInsertedTrainees[$id]);
             }
         }
-        
+
         // get the ids of the to be inserted trainees sorted by the birthday
-        $newTraineesIds = array_map(function($u){return $u->getId();},$toBeInsertedTrainees);
-        usort(
-            $newTraineesIds
-            , function($lhs, $rhs){
-                return $this->trainees[$lhs]->getStrBirthday() < $this->trainees[$rhs]->getStrBirthday() ? -1 : ($this->trainees[$lhs]->getStrBirthday() > $this->trainees[$rhs]->getStrBirthday() ? 1 : 0);
-            }
-        );
+        $newTraineesIds = array_map(function ($u) {
+            return $u->getId();
+        }, $toBeInsertedTrainees);
+        usort($newTraineesIds, function ($lhs, $rhs) {
+            return $this->trainees[$lhs]->getStrBirthday() <
+                $this->trainees[$rhs]->getStrBirthday()
+                ? -1
+                : ($this->trainees[$lhs]->getStrBirthday() >
+                $this->trainees[$rhs]->getStrBirthday()
+                    ? 1
+                    : 0);
+        });
         // $this->var_log(
         //     array_map(
         //         function($id){return $this->trainees[$id]->getStrBirthday()." ".$this->trainees[$id]->getFirstName();}
@@ -129,51 +187,99 @@ class PmElo{
         //     , "newTraineesBy B-Day"
         // );
 
-        // now we do a mergesort (step) 
+        // now we do a mergesort (step)
         $updatedRanking = [];
-        $idxNewTrainees = count($newTraineesIds)-1;
-        $idxRanking = count($cleanRanking)-1;
+        $idxNewTrainees = count($newTraineesIds) - 1;
+        $idxRanking = count($cleanRanking) - 1;
         // - while we can merge, we merge
-        while( ($idxRanking >= 0) && ($idxNewTrainees >= 0) ){
+        while ($idxRanking >= 0 && $idxNewTrainees >= 0) {
             // $this->var_log( [$idxRanking.", ".$idxNewTrainees=>$updatedRanking] );
             // $this->var_log(
             //     [$this->trainees[$cleanRanking[$idxRanking]]->getStrBirthday(), $this->trainees[$newTraineesIds[$idxRanking]]->getStrBirthday()]
             // );
-            if( 
-                $this->trainees[$cleanRanking[$idxRanking]]->getDateOfBirth()
-                > $this->trainees[$newTraineesIds[$idxNewTrainees]]->getDateOfBirth()
-            ){
+            if (
+                $this->trainees[$cleanRanking[$idxRanking]]->getDateOfBirth() >
+                $this->trainees[
+                    $newTraineesIds[$idxNewTrainees]
+                ]->getDateOfBirth()
+            ) {
                 // $this->var_log( $this->trainees[$cleanRanking[$idxRanking]]->getFirstName(), "merge ranking insert" );
                 array_unshift($updatedRanking, $cleanRanking[$idxRanking]);
-                $idxRanking-=1;
-            }else{
+                $idxRanking -= 1;
+            } else {
                 // $this->var_log( $this->trainees[$newTraineesIds[$idxNewTrainees]]->getFirstName(), "merge trainees insert" );
-                array_unshift($updatedRanking, $newTraineesIds[$idxNewTrainees]);
-                $idxNewTrainees-=1;
+                array_unshift(
+                    $updatedRanking,
+                    $newTraineesIds[$idxNewTrainees]
+                );
+                $idxNewTrainees -= 1;
             }
         }
         // $this->var_log(
         //     ["idxR ".$idxRanking." idxNT ".$idxNewTrainees=>[$cleanRanking, $newTraineesIds]]
         //     , "after merge"
         // );
-        while( $idxRanking >= 0 ){
+        while ($idxRanking >= 0) {
             // $this->var_log( $this->trainees[$cleanRanking[$idxRanking]]->getFirstName(), "rest ranking insert" );
             array_unshift($updatedRanking, $cleanRanking[$idxRanking]);
-            $idxRanking-=1;
+            $idxRanking -= 1;
         }
-        while( $idxNewTrainees >= 0 ){
+        while ($idxNewTrainees >= 0) {
             // $this->var_log( $this->trainees[$newTraineesIds[$idxNewTrainees]]->getFirstName(), "rest newTrainees insert" );
             array_unshift($updatedRanking, $newTraineesIds[$idxNewTrainees]);
-            $idxNewTrainees-=1;
+            $idxNewTrainees -= 1;
         }
         return $updatedRanking;
     }
 
-    public $log = ['error'=>[], 'warning'=>[], 'info'=>[]];
+    private function promote(
+        int $promoteeId,
+        int $promoteeRank,
+        int $degradeeId,
+        int $degradeeRank
+    ) {
+        // input sanitation
+        filterId($promoteeId);
+        filterId($promoteeRank);
+        filterId($degradeeId);
+        filterId($degradeeRank);
+        // check if both id are in the current fighter list
+        if (
+            array_key_exists($promoteeId, $this->fighters) &&
+            array_key_exists($degradeeId, $this->fighters)
+        ) {
+            // check their current rank
+            if (
+                $this->rankings[$promoteeRank] == $promoteeId &&
+                $this->rankings[$degradeeRank] == $degradeeId
+            ) {
+                // @todo check if they are rank neighbors in the fighter list
+                if (true) {
+                    // do the actual switch
+                    $this->rankings[$promoteeRank] = $degradeeId;
+                    $this->rankings[$degradeeRank] = $promoteeId;
+
+                    $this->saveRankings();
+                }
+            }
+        }
+        // save the updated ranking
+    }
+    // promotion means switching the position with another user
+    // id-s would already be sufficient, rank is just for controlling
+    function htmlPromoteButton(
+        int $promoteeId,
+        int $promoteeRank,
+        int $degradeeId,
+        int $degradeeRank
+    ) {
+    }
+
+    public $log = ["error" => [], "warning" => [], "info" => []];
     public $fighters = null;
     public $trainees = null;
     // list of id-s in the order of the current ranking
     public $rankings = null;
 
-    static $pmeloJson="./pmeloRanking.json";
-}
\ No newline at end of file
+    static $pmeloJson = "./pmeloRanking.json";
+}