Поиск по многомерному массиву

function showWay($paths, $way = null, $allNeedWays = null)
{
    if ($way === null) {
        reset($paths);
        $way[] = key($paths);
    }
 
    if ($paths[end($way)] === 'end') {
        return $way;
    }
    $allWays = $paths[end($way)];
    //$way[] = $allWays[0];
 
    foreach ($allWays as $stations) {
        $way[] = $stations;
        $newWay = showWay($paths, $way, $allNeedWays);
 
        if ($newWay !== null) {
            $allNeedWays[] = $newWay;
        }
    }
 
return showWay($paths, $way);
}
 
$paths = array(
    1 => [3,4],
    2 => [4],
    3 => [2],
    4 => [5],
    5 => 'end');
 
var_dump(showWay($paths)); // [1,3,2,4,5][1,4,5]

function showWay($paths, $way = null)
{
    if ($way === null) {
        reset($paths);
        $way[] = key($paths); // 1
    }
 
    $allStations = $paths[end($way)]; //3,4
 
 
    if ($allStations === 'end') {
        return $way; // 1,3,2,4,5 | 1,3,4,5
    }
 
    foreach ($allStations as $station) {
        $way[] = $station;
 
        $test = showWay($paths, $way);
 
        if ($test !== null) {
            var_dump($test);
        }
    }
    return null;
}
 
$paths = array(
    1 => [3, 4],
    2 => [4],
    3 => [2],
    4 => [5],
    5 => 'end');
 
print_r(showWay($paths));

<?php 
function first(&$array) { 
if (!is_array($array)) return &$array; 
if (!count($array)) return null; 
reset($array); 
return &$array[key($array)]; 
} 
 
function last(&$array) { 
if (!is_array($array)) return &$array; 
if (!count($array)) return null; 
end($array); 
return &$array[key($array)]; 
} 
?>