Enhancement: Use PSR-4 autoloader

Author: localheinz

autoload.php

@@ -0,0 +1,29 @@
+<?php
+
+/**
+ * @see https://github.com/php-fig/fig-standards/blob/a1a0674a742c9d07c5dd450209fb33b115ee7b40/accepted/PSR-4-autoloader-examples.md#closure-example
+ */
+spl_autoload_register(static function (string $class): void {
+    $prefix = 'phpweb\\';
+
+    $directory = __DIR__ . '/src/';
+
+    $length = strlen($prefix);
+
+    if (strncmp($prefix, $class, $length) !== 0) {
+        return;
+    }
+
+    $relativeClass = substr(
+        $class,
+        $length
+    );
+
+    $file = $directory . str_replace('\\', '/', $relativeClass) . '.php';
+
+    if (!file_exists($file)) {
+        return;
+    }
+
+    require $file;
+});

include/shared-manual.inc

@@ -23,7 +23,7 @@ $PGI = array(); $SIDEBAR_DATA = '';
 // User note display functions
 // =============================================================================
 
-require_once __DIR__ . '/../src/UserNotes/Sorter.php';
+require_once __DIR__ . '/../autoload.php';
 use phpweb\UserNotes\Sorter;
 
 // Print out all user notes for this manual page