Restructures demos.

demos/php/demo.php

@@ -0,0 +1,33 @@
+<?php
+
+// Install php, xdebug and the php debug extension for VS Code
+// (https://marketplace.visualstudio.com/items?itemName=felixfbecker.php-debug).
+
+// The Debug Visualizer has no support for PHP data extractors yet,
+// so to visualize data, your value must be a valid JSON string representing the data.
+// See readme for supported data schemas.
+
+$graph = [
+    "kind" => ["graph" => true],
+    "nodes" => [
+        ["id" => "1", "label" => "1"]
+    ],
+    "edges" => []
+];
+// Visualize "$visualize()"
+$visualize = function () use (&$graph) {
+    return json_encode($graph);
+};
+
+for ($i = 2; $i < 100; $i++) {
+    // add a node
+    $id = "" . $i;
+    array_push($graph["nodes"],
+        ["id" => $id, "label" => $id]);
+    // connects the node to a random edge
+    $targetId = "" . random_int(1, $i - 1);
+    array_push($graph["edges"],
+        ["from" => $id, "to" => "" . $targetId]);
+}
+
+echo "finished";