Introduce a depth parameter for normalization to limit stack nesting

src/Monolog/Formatter/JsonFormatter.php

@@ -135,8 +135,12 @@ class JsonFormatter extends NormalizerFormatter
      *
      * @return mixed
      */
-    protected function normalize($data)
+    protected function normalize($data, $depth = 0)
     {
+        if ($depth > 9) {
+            return 'Over 9 levels deep, aborting normalization';
+        }
+
         if (is_array($data) || $data instanceof \Traversable) {
             $normalized = array();
 
@@ -146,7 +150,7 @@ class JsonFormatter extends NormalizerFormatter
                     $normalized['...'] = 'Over 1000 items, aborting normalization';
                     break;
                 }
-                $normalized[$key] = $this->normalize($value);
+                $normalized[$key] = $this->normalize($value, $depth+1);
             }
 
             return $normalized;

src/Monolog/Formatter/NormalizerFormatter.php

@@ -55,8 +55,12 @@ class NormalizerFormatter implements FormatterInterface
         return $records;
     }
 
-    protected function normalize($data)
+    protected function normalize($data, $depth = 0)
     {
+        if ($depth > 9) {
+            return 'Over 9 levels deep, aborting normalization';
+        }
+
         if (null === $data || is_scalar($data)) {
             if (is_float($data)) {
                 if (is_infinite($data)) {
@@ -79,7 +83,7 @@ class NormalizerFormatter implements FormatterInterface
                     $normalized['...'] = 'Over 1000 items, aborting normalization';
                     break;
                 }
-                $normalized[$key] = $this->normalize($value);
+                $normalized[$key] = $this->normalize($value, $depth+1);
             }
 
             return $normalized;

src/Monolog/Formatter/WildfireFormatter.php

@@ -102,12 +102,12 @@ class WildfireFormatter extends NormalizerFormatter
         throw new \BadMethodCallException('Batch formatting does not make sense for the WildfireFormatter');
     }
 
-    protected function normalize($data)
+    protected function normalize($data, $depth = 0)
     {
         if (is_object($data) && !$data instanceof \DateTime) {
             return $data;
         }
 
-        return parent::normalize($data);
+        return parent::normalize($data, $depth);
     }
 }