fix: use Docker PHP-FPM to support sampling in conformance tests (#219)

tests/Conformance/FileLogger.php

@@ -0,0 +1,33 @@
+<?php
+
+/*
+ * This file is part of the official PHP MCP SDK.
+ *
+ * A collaboration between Symfony and the PHP Foundation.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Mcp\Tests\Conformance;
+
+use Psr\Log\AbstractLogger;
+
+final class FileLogger extends AbstractLogger
+{
+    public function __construct(
+        private readonly string $filePath,
+        private readonly bool $debug = false,
+    ) {
+    }
+
+    public function log($level, mixed $message, array $context = []): void
+    {
+        if (!$this->debug && 'debug' === $level) {
+            return;
+        }
+
+        $logMessage = \sprintf("[%s] %s\n", strtoupper($level), $message);
+        file_put_contents($this->filePath, $logMessage, \FILE_APPEND);
+    }
+}