docs

Author: staabm

doc/component/FAQ.markdown

@@ -51,3 +51,17 @@ obtained through `$node->getAttribute('next')`.
 
 `ParentConnectingVisitor` and `NodeConnectingVisitor` should not be used at the same time. The latter
 includes the functionality of the former.
+
+
+How can I limit the impact of cyclic references in the AST?
+-----
+
+NodeConnectingVisitor adds a parent reference, which introduces a cycle. This means that the AST can now only be collected by cycle garbage collector.
+This in turn can lead to performance and/or memory issues. 
+
+To break the cyclic references between AST nodes `NodeConnectingVisitor` supports a boolean `$weakReferences` constructor parameter.
+When set to `true`, all attributes added by `NodeConnectingVisitor` will be wrapped into a `WeakReference` object.
+
+After enabling this parameter, the parent node can be obtained through `$node->getAttribute('weak_parent')`,
+the previous node can be obtained through `$node->getAttribute('weak_previous')`, and the next node can be
+obtained through `$node->getAttribute('weak_next')`.

lib/PhpParser/NodeVisitor/NodeConnectingVisitor.php

@@ -9,10 +9,12 @@
  * Visitor that connects a child node to its parent node
  * as well as its sibling nodes.
  *
- * On the child node, the parent node can be accessed through
+ * With <code>$weakReferences=false</code> on the child node, the parent node can be accessed through
  * <code>$node->getAttribute('parent')</code>, the previous
  * node can be accessed through <code>$node->getAttribute('previous')</code>,
  * and the next node can be accessed through <code>$node->getAttribute('next')</code>.
+ *
+ * With <code>$weakReferences=true</code> attribute names are prefixed by "weak_", e.g. "weak_parent".
  */
 final class NodeConnectingVisitor extends NodeVisitorAbstract {
     /**

lib/PhpParser/NodeVisitor/ParentConnectingVisitor.php

@@ -11,8 +11,10 @@
 /**
  * Visitor that connects a child node to its parent node.
  *
- * On the child node, the parent node can be accessed through
+ * With <code>$weakReferences=false</code> on the child node, the parent node can be accessed through
  * <code>$node->getAttribute('parent')</code>.
+ *
+ * With <code>$weakReferences=true</code> the attribute name is "weak_parent" instead.
  */
 final class ParentConnectingVisitor extends NodeVisitorAbstract {
     /**