Create page cache skeleton

Author: john-shaffer

src/drop-in/advanced-cache.php

@@ -0,0 +1,46 @@
+<?php
+
+/**
+ * Page cache for WordPress
+ * Must be placed in wp-content/advanced-cache.php
+ * It will be loaded when WP_CACHE is true
+ * See https://developer.wordpress.org/reference/functions/_get_dropins/
+ * 
+ * This runs before plugins and themes and most WordPress
+ * code runs, so we only have access to a limited set of
+ * WordPress functions.
+ */
+
+class StaticDeployPageCache {
+    function capture_output(): void {
+        $buffering = ob_start([$this, 'receive_output']);
+
+        if ($buffering === false) {
+            error_log('Output buffering failed');
+        }
+    }
+
+    /**
+     * Receives the PHP output, which should be the body
+     * of an HTTP response, and caches it.
+     * 
+     * This can be called whenever output is flushed,
+     * and not necessarily when output is finished.
+     *
+     * This is the callback provided to ob_start
+     * https://www.php.net/manual/en/function.ob-start.php
+     * 
+     * The return value determines the output that is sent
+     * to the client.
+     *  - A string value: Sent instead of the buffer
+     *  - false: Sends the original output buffer contents
+     *  - true: Sends an empty string instead of the buffer
+     */
+    function receive_output(
+        string $buffer
+    ): string|bool {
+        return false;
+    }
+}
+
+new StaticDeployPageCache()->capture_output();