var_export 没法解决循环引用问题，部分情况会导致内存溢出

src/functions.php

@@ -453,7 +453,7 @@ if (!function_exists('putLog')) {
         $stream = make(StreamHandler::class, [$dir . $filename, Logger::WARNING]);
         $fire = make(FirePHPHandler::class);
         if (is_array($output)) {
-            $output = var_export($output, true);
+            $output = print_r($output, true);
         }
         $output = '[ ' . date('Y-m-d H:i:s', time()) . ' ] --- ' . $output;
         $formatter = new LineFormatter($output . "\r\n");