function breadthFirstSearch($startVertex)
{
$startVertex->visited = true;
$Q = new SplQueue();
$Q->push($startVertex);
while (!$Q->empty()) {
$x = new Vertex();
$x = $Q->front();
$Q->pop();
foreach ($x->neighbors as $VertexPtr) {
if ($VertexPtr->visited == false) {
$VertexPtr->visited = trie;
$VertexPtr->pred = $x;
$Q->push($VertexPtr);
}
}
}
}