src/Language/Visitor.php
public static function visit($root, $visitor, $keyMap = null)
    {
        $visitorKeys = $keyMap ?: self::$visitorKeys;

        $stack     = null;
        $inArray   = $root instanceof NodeList || is_array($root);
        $keys      = [$root];
        $index     = -1;
        $edits     = [];
        $parent    = null;
        $path      = [];
        $ancestors = [];
        $newRoot   = $root;

        $UNDEFINED = null;

        do {
            $index++;
            $isLeaving = $index === count($keys);
            $key       = null;
            $node      = null;
            $isEdited  = $isLeaving && count($edits) !== 0;

            if ($isLeaving) {
                $key    = ! $ancestors ? $UNDEFINED : $path[count($path) - 1];
                $node   = $parent;
                $parent = array_pop($ancestors);

                if ($isEdited) {
                    if ($inArray) {
                        // $node = $node; // arrays are value types in PHP
                        if ($node instanceof NodeList) {
                            $node = clone $node;
                        }
                    } else {
                        $node = clone $node;
                    }
                    $editOffset = 0;
                    for ($ii = 0; $ii < count($edits); $ii++) {
                        $editKey   = $edits[$ii][0];
                        $editValue = $edits[$ii][1];

                        if ($inArray) {
                            $editKey -= $editOffset;
                        }
                        if ($inArray && $editValue === null) {
                            if ($node instanceof NodeList) {
                                $node->splice($editKey, 1);
                            } else {
                                array_splice($node, $editKey, 1);
                            }
                            $editOffset++;
                        } else {
                            if ($node instanceof NodeList || is_array($node)) {
                                $node[$editKey] = $editValue;
                            } else {
                                $node->{$editKey} = $editValue;
                            }
                        }
                    }
                }
                $index   = $stack['index'];
                $keys    = $stack['keys'];
                $edits   = $stack['edits'];
                $inArray = $stack['inArray'];
                $stack   = $stack['prev'];
            } else {
                $key  = $parent !== null ? ($inArray ? $index : $keys[$index]) : $UNDEFINED;
                $node = $parent !== null ? ($parent instanceof NodeList || is_array($parent) ? $parent[$key] : $parent->{$key}) : $newRoot;
                if ($node === null || $node === $UNDEFINED) {
                    continue;
                }
                if ($parent !== null) {
                    $path[] = $key;
                }
            }

            $result = null;
            if (! $node instanceof NodeList && ! is_array($node)) {
                if (! ($node instanceof Node)) {
                    throw new Exception('Invalid AST Node: ' . json_encode($node));
                }

                $visitFn = self::getVisitFn($visitor, $node->kind, $isLeaving);

                if ($visitFn) {
                    $result    = call_user_func($visitFn, $node, $key, $parent, $path, $ancestors);
                    $editValue = null;

                    if ($result !== null) {
                        if ($result instanceof VisitorOperation) {
                            if ($result->doBreak) {
                                break;
                            }
                            if (! $isLeaving && $result->doContinue) {
                                array_pop($path);
                                continue;
                            }
                            if ($result->removeNode) {
                                $editValue = null;
                            }
                        } else {
                            $editValue = $result;
                        }

                        $edits[] = [$key, $editValue];
                        if (! $isLeaving) {
                            if (! ($editValue instanceof Node)) {
                                array_pop($path);
                                continue;
                            }

                            $node = $editValue;
                        }
                    }
                }
            }

            if ($result === null && $isEdited) {
                $edits[] = [$key, $node];
            }

            if ($isLeaving) {
                array_pop($path);
            } else {
                $stack   = [
                    'inArray' => $inArray,
                    'index'   => $index,
                    'keys'    => $keys,
                    'edits'   => $edits,
                    'prev'    => $stack,
                ];
                $inArray = $node instanceof NodeList || is_array($node);

                $keys  = ($inArray ? $node : $visitorKeys[$node->kind]) ?: [];
                $index = -1;
                $edits = [];
                if ($parent !== null) {
                    $ancestors[] = $parent;
                }
                $parent = $node;
            }
        } while ($stack);

        if (count($edits) !== 0) {
            $newRoot = $edits[0][1];
        }

        return $newRoot;
    }
public static function visit($root, $visitor, $keyMap = null)
    {
        $visitorKeys = $keyMap ?: self::$visitorKeys;

        $stack     = null;
        $inArray   = $root instanceof NodeList || is_array($root);
        $keys      = [$root];
        $index     = -1;
        $edits     = [];
        $parent    = null;
        $path      = [];
        $ancestors = [];
        $newRoot   = $root;

        $UNDEFINED = null;

        do {
            $index++;
            $isLeaving = $index === count($keys);
            $key       = null;
            $node      = null;
            $isEdited  = $isLeaving && count($edits) !== 0;

            if ($isLeaving) {
                $key    = ! $ancestors ? $UNDEFINED : $path[count($path) - 1];
                $node   = $parent;
                $parent = array_pop($ancestors);

                if ($isEdited) {
                    if ($inArray) {
                        // $node = $node; // arrays are value types in PHP
                        if ($node instanceof NodeList) {
                            $node = clone $node;
                        }
                    } else {
                        $node = clone $node;
                    }
                    $editOffset = 0;
                    for ($ii = 0; $ii < count($edits); $ii++) {
                        $editKey   = $edits[$ii][0];
                        $editValue = $edits[$ii][1];

                        if ($inArray) {
                            $editKey -= $editOffset;
                        }
                        if ($inArray && $editValue === null) {
                            if ($node instanceof NodeList) {
                                $node->splice($editKey, 1);
                            } else {
                                array_splice($node, $editKey, 1);
                            }
                            $editOffset++;
                        } else {
                            if ($node instanceof NodeList || is_array($node)) {
                                $node[$editKey] = $editValue;
                            } else {
                                $node->{$editKey} = $editValue;
                            }
                        }
                    }
                }
                $index   = $stack['index'];
                $keys    = $stack['keys'];
                $edits   = $stack['edits'];
                $inArray = $stack['inArray'];
                $stack   = $stack['prev'];
            } else {
                $key  = $parent !== null ? ($inArray ? $index : $keys[$index]) : $UNDEFINED;
                $node = $parent !== null ? ($parent instanceof NodeList || is_array($parent) ? $parent[$key] : $parent->{$key}) : $newRoot;
                if ($node === null || $node === $UNDEFINED) {
                    continue;
                }
                if ($parent !== null) {
                    $path[] = $key;
                }
            }

            $result = null;
            if (! $node instanceof NodeList && ! is_array($node)) {
                if (! ($node instanceof Node)) {
                    throw new Exception('Invalid AST Node: ' . json_encode($node));
                }

                $visitFn = self::getVisitFn($visitor, $node->kind, $isLeaving);

                if ($visitFn) {
                    $result    = call_user_func($visitFn, $node, $key, $parent, $path, $ancestors);
                    $editValue = null;

                    if ($result !== null) {
                        if ($result instanceof VisitorOperation) {
                            if ($result->doBreak) {
                                break;
                            }
                            if (! $isLeaving && $result->doContinue) {
                                array_pop($path);
                                continue;
                            }
                            if ($result->removeNode) {
                                $editValue = null;
                            }
                        } else {
                            $editValue = $result;
                        }

                        $edits[] = [$key, $editValue];
                        if (! $isLeaving) {
                            if (! ($editValue instanceof Node)) {
                                array_pop($path);
                                continue;
                            }

                            $node = $editValue;
                        }
                    }
                }
            }

            if ($result === null && $isEdited) {
                $edits[] = [$key, $node];
            }

            if ($isLeaving) {
                array_pop($path);
            } else {
                $stack   = [
                    'inArray' => $inArray,
                    'index'   => $index,
                    'keys'    => $keys,
                    'edits'   => $edits,
                    'prev'    => $stack,
                ];
                $inArray = $node instanceof NodeList || is_array($node);

                $keys  = ($inArray ? $node : $visitorKeys[$node->kind]) ?: [];
                $index = -1;
                $edits = [];
                if ($parent !== null) {
                    $ancestors[] = $parent;
                }
                $parent = $node;
            }
        } while ($stack);

        if (count($edits) !== 0) {
            $newRoot = $edits[0][1];
        }

        return $newRoot;
    }
Visit the AST (see class description for details)

@param Node|ArrayObject|stdClass $root
@param callable[]                $visitor
@param mixed[]|null              $keyMap

@return Node|mixed

@throws Exception

@api