Add BasePathMiddleware for subdirectory deployments

Slim/Middleware/BasePathMiddleware.php

@@ -0,0 +1,126 @@
+<?php
+
+/**
+ * Slim Framework (https://slimframework.com)
+ *
+ * @license https://github.com/slimphp/Slim/blob/4.x/LICENSE.md (MIT License)
+ */
+
+declare(strict_types=1);
+
+namespace Slim\Middleware;
+
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Server\MiddlewareInterface;
+use Psr\Http\Server\RequestHandlerInterface;
+
+use function array_pop;
+use function dirname;
+use function end;
+use function explode;
+use function implode;
+use function is_string;
+use function ltrim;
+use function rtrim;
+use function str_starts_with;
+use function strlen;
+use function substr;
+
+/**
+ * Middleware to handle applications running in a subdirectory.
+ *
+ * Strips the base path from the request URI so routes can be defined
+ * without the base path prefix.
+ *
+ * @package Slim\Middleware
+ * @api
+ */
+class BasePathMiddleware implements MiddlewareInterface
+{
+    /**
+     * @var string The base path to strip (e.g., '/myapp')
+     */
+    private string $basePath;
+
+    /**
+     * @param string $basePath The base path to strip (e.g., '/myapp')
+     */
+    public function __construct(string $basePath = '')
+    {
+        $this->basePath = rtrim($basePath, '/');
+    }
+
+    /**
+     * Create middleware with auto-detected base path from request server params.
+     *
+     * Detects the base path from SCRIPT_NAME server parameter.
+     * If SCRIPT_NAME points to /public/index.php, it strips the /public part.
+     *
+     * @param ServerRequestInterface $request The request to detect base path from
+     * @return self
+     */
+    public static function fromRequest(ServerRequestInterface $request): self
+    {
+        $serverParams = $request->getServerParams();
+        $scriptName = $serverParams['SCRIPT_NAME'] ?? '';
+
+        if (!is_string($scriptName) || $scriptName === '') {
+            return new self('');
+        }
+
+        // Get the directory of the script
+        $basePath = rtrim(dirname($scriptName), '/');
+
+        // If the script is in /public directory, strip it
+        if (str_starts_with($basePath, '/')) {
+            $parts = explode('/', $basePath);
+            if (end($parts) === 'public') {
+                array_pop($parts);
+                $basePath = implode('/', $parts);
+            }
+        }
+
+        return new self($basePath);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    #[\Override]
+    public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
+    {
+        // If base path is empty, skip processing
+        if ($this->basePath === '') {
+            return $handler->handle($request);
+        }
+
+        $uri = $request->getUri();
+        $path = $uri->getPath();
+
+        // If base path doesn't match, skip
+        if (!str_starts_with($path, $this->basePath . '/')) {
+            // Special case: exact match on base path (e.g., /myapp -> /)
+            if ($path !== $this->basePath) {
+                return $handler->handle($request);
+            }
+        }
+
+        // Strip the base path
+        $newPath = (string) substr($path, strlen($this->basePath));
+
+        // Ensure path starts with /
+        if ($newPath === '' || !str_starts_with($newPath, '/')) {
+            $newPath = '/' . ltrim($newPath, '/');
+        }
+
+        // Create new request with modified URI
+        $newUri = $uri->withPath($newPath);
+        $request = $request->withUri($newUri);
+
+        // Store original base path in attribute (useful for URL generation)
+        $request = $request->withAttribute('basePath', $this->basePath);
+
+        return $handler->handle($request);
+    }
+}