Seems fine to me.

<?php
include("systems/systems.php");
$PossiblePaths = array();
$PathCount = 0;
function PlanRoute($nextID, $targetID, $history = null, $depth = 0){
    global $Systems, $PossiblePaths, $PathCount;
    $potentials = $Systems[$nextID]["JumpsTo"];
    $history[] = $nextID;
    if(!empty($potentials)){
        if(!in_array($targetID, $potentials)){ //Not at end location, therefore try next location
            $depth++;
            if($depth < 20){
                foreach($potentials as $value){
                    if(!in_array($value, $history)){
                        $path = PlanRoute($value, $targetID, $history, $depth);
                        if(isset($path)){
                            $PathCount++;
                            $PossiblePaths[$PathCount] = $path;
                        }
                    }
                }
            }else{
                return;
            }
        }else{
            foreach($history as $SystemID){
                $Trip[] = $SystemID;
            }
            $Trip[] = $targetID;
            return $Trip;
        }
    }
}
function SortByElementCount($a, $b){
    if(count($a) == count($b)){
        return 0;
    }
    return (count($a) < count($b)) ? -1 : 1;
}

function SortBySecurity($a, $b){
    $countA = count($a);
    $countB = count($b);
    foreach($a as $ae){
        $averageA += $Systems[$ae]['Sec']/$countA;
    }
    foreach($b as $be){
        $averageB += $Systems[$be]['Sec']/$countB;
    }
    if($averageB == $averageA){
        return 0;
    }
    return ($averageA < $averageB) ? -1 : 1;
}
$origin = 30000001; //Get starting point
$target = 30000142; //Get end point
echo "Planning jump route from ".$Systems[$origin]['Name']." to ".$Systems[$target]['Name']."<br><br>\n";
$path = PlanRoute($origin, $target);
if(isset($path)){
    usort($path, "SortByElementCount");
    var_dump($path);
}
if(!empty($PossiblePaths)){
    usort($PossiblePaths, "SortByElementCount");
    var_dump($PossiblePaths);
}
?>