Djikstra Algo in PHP

dijkstra.php

<?php

$graph = [
  "start" => [
    "a" => 6,
    "b" => 2,
  ],
  "a" => [
    "end" => 1
  ],
  "b" => [
    "a" => 3,
    "end" => 5
  ],
  "end" => [],
];

$costs = [
  "a" => 6,
  "b" => 2,
  "end" => INF,
];

$parents = [
  "a" => "start",
  "b" => "start",
  "end" => null,
];

$processed = [];

function findLowestCostNode($costs, $processed) {
  $lowestCost = INF;
  $nodeWithLowestCost = null;

  foreach ($costs as $n => $nCost) {
    if ($nCost < $lowestCost && !in_array($n, $processed)) {
      $lowestCost = $nCost;
      $nodeWithLowestCost = $n;
    }
  }

  return $nodeWithLowestCost;
}

$node = findLowestCostNode($costs, $processed);

while ($node !== null) {
  $cost = $costs[$node];
  $neighbors = $graph[$node];

  foreach ($neighbors as $n => $nCost) {
    $newCost = $cost + $nCost;

    if ($costs[$n] > $newCost) {
      $costs[$n] = $newCost;
      $parents[$n] = $node;
    }
  }

  $processed[] = $node;
  $node = findLowestCostNode($costs, $processed);
}

function getFinalPath($parents) {
  $path = [];
  $node = "end";

  while($node !== "start") {
    array_unshift($path, $node);
    $node = $parents[$node];
  }

  array_unshift($path, "start");

  return implode(' -> ', $path);
}

echo "=== LOWEST COST UNTIL END ===".PHP_EOL;
print_r($costs["end"]);
echo PHP_EOL;
echo "=== SHORTEST PATH ===".PHP_EOL;
print_r(getFinalPath($parents));