<?php

/**
 * @template-covariant TKey
 * @template-covariant TValue
 *
 * @template-extends Traversable<TKey, TValue>
 */
interface IteratorAggregate extends Traversable {

    /**
     * @return Traversable<TKey, TValue> An instance of an object implementing Iterator or Traversable
     */
    public function getIterator();
}

/**
 * @template-covariant TKey
 * @template-covariant TValue
 *
 * @template-extends Traversable<TKey, TValue>
 */
interface Iterator extends Traversable {

    /**
     * @return TValue|null returns current value or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function current();

    /**
     * @return void Any returned value is ignored.
     */
    public function next();

    /**
     * @return TKey|null current key or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function key();

    /**
     * @return bool The return value will be casted to boolean and then evaluated.
     *              Returns true on success or false on failure.
     */
    public function valid();

    /**
     * @return void Any returned value is ignored.
     */
    public function rewind();
}

/**
 * @template-covariant TKey
 * @template-covariant TValue
 *
 * @template-extends Iterator<TKey, TValue>
 */
interface OuterIterator extends Iterator {
    /**
     * @return Iterator<TKey, TValue>
     */
    public function getInnerIterator();
}

/**
 * @template-covariant TKey
 * @template-covariant TValue
 *
 * @template-extends Iterator<TKey, TValue>
 */
interface RecursiveIterator extends Iterator {

    /**
     * @return bool true if the current entry can be iterated over, otherwise returns false.
     */
    public function hasChildren();

    /**
     * @return RecursiveIterator<TKey, TValue> An iterator for the current entry.
     */
    public function getChildren();
}

/**
 * @template-covariant TKey
 * @template-covariant TValue
 * @template-extends Iterator<TKey, TValue>
 */
interface SeekableIterator extends Iterator {
    /**
     * Seeks to a position
     * @link https://php.net/manual/en/seekableiterator.seek.php
     *
     * @param int $position The position to seek to.
     * @return void
     *
     * @since 5.1.0
     */
    public function seek($position);
}

/**
 * @template-covariant TKey
 * @template-covariant TValue
 * @template TIterator as Traversable<TKey, TValue>
 *
 * @template-implements OuterIterator<TKey, TValue>
 *
 * @mixin TIterator
 */
class IteratorIterator implements OuterIterator {
    /**
     * @param TIterator $iterator
     */
    public function __construct(Traversable $iterator) {}

    /**
     * @return TValue|null current value or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function current() {}

    /**
     * @return TKey|null current key value or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function key() {}
}

/**
 * @template TKey
 * @template TValue
 * @template TIterator as Traversable<TKey, TValue>
 *
 * @template-extends IteratorIterator<TKey, TValue>
 */
class AppendIterator extends IteratorIterator {
    public function __construct(){}

    /**
     * @param TIterator $iterator
     * @return void
     */
    public function append(Iterator $iterator) {}

    /**
     * @return ArrayIterator<TKey, TValue>
     */
    public function getArrayIterator() {}

    /**
     * @return int
     */
    public function getIteratorIndex() {}

    /**
     * @return TValue|null current value or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function current() {}

    /**
     * @return TKey|null current value or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function key() {}
}

/**
 * @template TKey as array-key
 * @template TValue
 * @template-implements SeekableIterator<TKey, TValue>
 * @template-implements ArrayAccess<TKey, TValue>
 */
class ArrayIterator implements SeekableIterator, ArrayAccess, Serializable, Countable {
    const STD_PROP_LIST = 1;
    const ARRAY_AS_PROPS = 2;

    /**
     * @param array<TKey, TValue> $array The array or object to be iterated on.
     * @param int-mask-of<static::*> $flags Flags to control the behaviour of the ArrayObject object.
     */
    public function __construct($array = array(), $flags = 0) { }

    /**
     * @param TKey $index The offset being checked.
     * @return bool true if the offset exists, otherwise false
     */
    public function offsetExists($index) { }

    /**
     * @param TKey $index The offset to get the value from.
     * @return TValue|null The value at offset index, null when accessing invalid indexes
     * @psalm-ignore-nullable-return
     */
    public function offsetGet($index) { }

    /**
     * @param TKey $index The index to set for.
     * @param TValue $newval The new value to store at the index.
     * @return void
     */
    public function offsetSet($index, $newval) { }

    /**
     * @param TKey $index The offset to unset.
     * @return void
     */
    public function offsetUnset($index) { }

    /**
     * @param TValue $value The value to append.
     * @return void
     */
    public function append($value) { }

    /**
     * @return array<TKey, TValue> A copy of the array, or array of public properties
     *                             if ArrayIterator refers to an object.
     */
    public function getArrayCopy() { }

    /**
     * @return int The number of elements or public properties in the associated
     *             array or object, respectively.
     */
    public function count() { }

    /**
     * @return int-mask-of<self::*> The current flags.
     */
    public function getFlags() { }

    /**
     * @param int-mask-of<self::*> $flags bitmask
     * @return void
     */
    public function setFlags($flags) { }

    /**
     * @return void
     */
    public function asort() { }

    /**
     * @return void
     */
    public function ksort() { }

    /**
     * @param callable(TValue,TValue):int $cmp_function The compare function used for the sort.
     * @return void
     */
    public function uasort($cmp_function) { }

    /**
     * @param callable(TKey,TKey):int $cmp_function The compare function used for the sort.
     * @return void
     */
    public function uksort($cmp_function) { }

    /**
     * @return void
     */
    public function natsort() { }

    /**
     * @return void
     */
    public function natcasesort() { }

    /**
     * @param string $serialized The serialized ArrayIterator object to be unserialized.
     * @return void
     */
    public function unserialize($serialized) { }

    /**
     * @return string The serialized ArrayIterator
     */
    public function serialize() { }

    /**
     * @return void
     */
    public function rewind() { }

    /**
     * @return TValue|null current value or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function current() { }

    /**
     * @return TKey|null The current array key or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function key() { }

    /**
     * @return void
     */
    public function next() { }

    /**
     * @return bool
     */
    public function valid() { }

    /**
     * @param int $position The position to seek to.
     * @return void
     */
    public function seek($position) { }
}

/**
 * @template-covariant TKey
 * @template-covariant TValue
 *
 * @template-extends IteratorIterator<TKey, TValue>
 */
class FilterIterator extends IteratorIterator {
    /** @return bool */
    abstract public function accept();

    /**
     * @return TValue Can return any type.
     */
    public function current() {}

    /**
     * @return TKey scalar on success, or null on failure.
     */
    public function key() {}
}

/**
 * @template-covariant TKey
 * @template-covariant TValue
 *
 * @template-implements OuterIterator<TKey, TValue>
 * @template-implements ArrayAccess<TKey, TValue>
 *
 * @template-extends IteratorIterator<TKey, TValue>
 */
class CachingIterator extends IteratorIterator implements OuterIterator , ArrayAccess , Countable  {
    const CALL_TOSTRING = 1 ;
    const CATCH_GET_CHILD = 16 ;
    const TOSTRING_USE_KEY = 2 ;
    const TOSTRING_USE_CURRENT = 4 ;
    const TOSTRING_USE_INNER = 8 ;
    const FULL_CACHE = 256 ;
    
    /**
     * @param Iterator<TKey, TValue> $iterator
     * @param int-mask-of<self::*> $flags
     */
    public function __construct(Iterator $iterator, int $flags = self::CALL_TOSTRING) {}

    /** @return bool */
    public function hasNext () {}

    /**
     * @return TValue|null current value or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function current() {}

    /**
     * @return TKey|null current key or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function key() {}
}

/**
 * @template-covariant TKey
 * @template-covariant TValue
 *
 * @template-implements OuterIterator<TKey, TValue>
 *
 * @template-extends FilterIterator<TKey, TValue>
 */
class CallbackFilterIterator extends FilterIterator implements OuterIterator  {
    /**
     * @param Iterator<TKey, TValue> $iterator
     * @param callable(TValue, TKey, Iterator<TKey, TValue>): bool $callback
     */
    public function __construct(Iterator $iterator, callable $callback) {}

    /**
     * @return TValue|null current value or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function current() {}

    /**
     * @return TKey|null current key or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function key() {}
}

/**
 * @template-implements SeekableIterator<int, DirectoryIterator>
 */
class DirectoryIterator extends SplFileInfo implements SeekableIterator {

    public function __construct(string $path){}

    /**
     * @return self
     */
    public function current() {}
    /**
     * @return int|false
     * @psalm-ignore-falsable-return
     */
    public function key() {}

    /**
     * @return void
     */
    public function next(){}
    /**
     * @return void
     */
    public function rewind(){}

    /**
     * @param int $position
     */
    public function seek($position) {}

    /**
     * @return bool
     */
    public function valid(){}
}

/**
 * @template-implements Iterator<never, never>
 */
class EmptyIterator implements Iterator {
    /**
     * @return never
     */
    public function current() {}
    /**
     * @return never
     */
    public function key() {}
    /**
     * @return void
     */
    public function next() {}
    /**
     * @return void
     */
    public function rewind() {}

    /**
     * @return false
     */
    public function valid() {}
}

/**
 * @template-extends SeekableIterator<string, FilesystemIterator|SplFileInfo|string>
 */
class FilesystemIterator extends DirectoryIterator
{
    const CURRENT_AS_PATHNAME = 32;
    const CURRENT_AS_FILEINFO = 0;
    const CURRENT_AS_SELF = 16;
    const CURRENT_MODE_MASK = 240;
    const KEY_AS_PATHNAME = 0;
    const KEY_AS_FILENAME = 256;
    const FOLLOW_SYMLINKS = 512;
    const KEY_MODE_MASK = 3840;
    const NEW_CURRENT_AND_KEY = 256;
    const SKIP_DOTS = 4096;
    const UNIX_PATHS = 8192;

    /**
     * @param int-mask<self::CURRENT_AS_PATHNAME,self::CURRENT_AS_FILEINFO,self::CURRENT_AS_SELF,self::KEY_AS_PATHNAME,self::KEY_AS_FILENAME,self::FOLLOW_SYMLINKS,self::NEW_CURRENT_AND_KEY,self::SKIP_DOTS,self::UNIX_PATHS> $flags
     */
    public function __construct(string $path, int $flags = self::KEY_AS_PATHNAME|self::CURRENT_AS_FILEINFO|self::SKIP_DOTS) {}

    /**
     * @return FilesystemIterator|SplFileInfo|string|null
     * @psalm-ignore-nullable-return
     */
    public function current() {}
    /**
     * @return int-mask<self::CURRENT_AS_PATHNAME,self::CURRENT_AS_FILEINFO,self::CURRENT_AS_SELF,self::KEY_AS_PATHNAME,self::KEY_AS_FILENAME,self::FOLLOW_SYMLINKS,self::NEW_CURRENT_AND_KEY,self::SKIP_DOTS,self::UNIX_PATH>
     */
    public function getFlags() {}

    /**
     * @param int-mask<self::CURRENT_AS_PATHNAME,self::CURRENT_AS_FILEINFO,self::CURRENT_AS_SELF,self::KEY_AS_PATHNAME,self::KEY_AS_FILENAME,self::FOLLOW_SYMLINKS,self::NEW_CURRENT_AND_KEY,self::SKIP_DOTS,self::UNIX_PATH> $flags
     * @return void
     */
    public function setFlags($flags) {}
    /**
     * @return string|null
     * @psalm-ignore-nullable-return
     */
    public function key() {}
}


/**
 * @template-extends SeekableIterator<string, GlobIterator|SplFileInfo|string>
 */
class GlobIterator extends FilesystemIterator implements Countable {
    /**
     * @return int
     */
    public function count() {}
}

/**
 * @template-covariant TKey
 * @template-covariant TValue
 *
 * @template-extends IteratorIterator<TKey, TValue>
 */
class InfiniteIterator extends IteratorIterator {
    /**
     * @param Iterator<TKey, TValue> $iterator
     */
    public function __construct(Iterator $iterator) {}

    /**
     * @return TValue|null current value or null if iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function current() {}

    /**
     * @return TKey|null current key or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function key() {}
}

/**
 * @template-covariant TKey
 * @template-covariant TValue
 *
 * @template-implements OuterIterator<TKey, TValue>
 *
 * @template-extends IteratorIterator<TKey, TValue>
 */
class LimitIterator extends IteratorIterator implements OuterIterator {
    /**
     * @param Iterator<TKey, TValue> $iterator
     */
    public function __construct(Iterator $iterator, int $offset = 0, int $count = -1) {}

    /**
     * @return TValue|null current value or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function current() {}

    /**
     * @return TKey|null current key or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function key() {}
}


/**
 * @template-covariant TKey
 * @template-covariant TValue
 *
 * @template-extends IteratorIterator<TKey, TValue>
 */
class NoRewindIterator extends IteratorIterator {
    /**
     * @param Iterator<TKey, TValue> $iterator
     */
    public function __construct(Iterator $iterator) {}

    /**
     * @return TValue|null current value or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function current() {}

    /**
     * @return TKey|null current value or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function key() {}
}

/**
 *
 * @template-covariant TKey
 * @template-covariant TValue
 *
 * @template-implements Iterator<TKey, TValue>
 */
class MultipleIterator implements Iterator {
    const MIT_NEED_ANY = 0 ;
    const MIT_NEED_ALL = 1 ;
    const MIT_KEYS_NUMERIC = 0 ;
    const MIT_KEYS_ASSOC = 2 ;

    /**
     * @param int-mask-of<self::MIT_*> $flags
     */
    public function __construct (int $flags = 0) {}
    /**
     * @param Iterator<TKey,TValue> $iterator
     * @param string|int $infos
     * @return void
     */
    public function attachIterator(Iterator $iterator, $infos = '') {}
    /**
     * @param Iterator<TKey, TValue> $iterator
     * @return bool
     */
    public function containsIterator(Iterator $iterator) {}

    /**
     * @return int
     */
    public function countIterators() {}
    /**
     * nullable values are returned when MIT_NEED_ANY is set
     * and one of the iterators is already drained.
     * When MIT_NEED_ALL is set and one of the iterators
     * is already drained, `current()` throws
     *
     * @return array<array-key, TValue|null>
     */
    public function current() {}
    /**
     * @param Iterator<TKey,TValue> $iterator
     * @return void
     */
    public function detachIterator(Iterator $iterator) {}
    /**
     * @return int-mask-of<self::MIT_*>
     */
    public function getFlags() {}
    /**
     * @return array<array-key, TValue|null>
     */
    public function key() {}
    /**
     * @param int-mask-of<self::MIT_*> $flags
     * @return void
     */
    public function setFlags( int $flags ) {}
}

/**
 * @template TKey
 * @template TValue
 *
 * @template-extends FilterIterator<TKey, TValue>
 * @template-implements RecursiveIterator<TKey, TValue>
 */
abstract class RecursiveFilterIterator extends FilterIterator implements RecursiveIterator {

    /**
     * @param RecursiveIterator<TKey, TValue> $iterator
     */
    public function __construct(RecursiveIterator $iterator) {}
    /**
     * @return RecursiveFilterIterator<TKey, TValue>
     */
    public function getChildren() {}

    /**
     * @return bool
     */
    public function hasChildren() {}

    /**
     * @return TValue|null current value or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function current() {}

    /**
     * @return TKey|null current value or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function key() {}
}

/**
 * @template TKey
 * @template TValue
 *
 * @template-extends RecursiveFilterIterator<TKey, TValue>
 */
class ParentIterator extends RecursiveFilterIterator implements RecursiveIterator, OuterIterator {

    /**
     * @return bool
     */
    public function accept() {}
    /**
     * @param RecursiveIterator<TKey, TValue> $iterator
     */
    public function __construct(RecursiveIterator $iterator) {}
    /**
     * @return ParentIterator<TKey,TValue>
     */
    public function getChildren() {}

    /**
     * @return bool
     */
    public function hasChildren() {}
    /**
     * @return void
     */
    public function next() {}
    /**
     * @return void
     */
    public function rewind() {}

    /**
     * @return TValue|null current value or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function current() {}

    /**
     * @return TKey|null current key or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function key() {}
}

/**
 * @template TKey
 * @template TValue
 *
 * @template-implements RecursiveIterator<TKey, TValue>
 * @template-extends ArrayIterator<TKey, TValue>
 */
class RecursiveArrayIterator extends ArrayIterator implements RecursiveIterator {
    const STD_PROP_LIST = 1 ;
    const ARRAY_AS_PROPS = 2 ;
    const CHILD_ARRAYS_ONLY = 4 ;

    /**
     * @return RecursiveArrayIterator<TKey, TValue>
     */
    public function getChildren() {}

    /**
     * @return bool
     */
    public function hasChildren() {}
    /**
     * @return TValue|null current value or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function current() {}

    /**
     * @return TKey|null current key or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function key() {}
}

/**
 * @template TKey
 * @template TValue
 *
 * @template-implements RecursiveIterator<TKey, TValue>
 * @template-extends ArrayIterator<TKey, TValue>
 */
class RecursiveCachingIterator extends CachingIterator implements RecursiveIterator {

    const CALL_TOSTRING = 1 ;
    const CATCH_GET_CHILD = 16 ;
    const TOSTRING_USE_KEY = 2 ;
    const TOSTRING_USE_CURRENT = 4 ;
    const TOSTRING_USE_INNER = 8 ;
    const FULL_CACHE = 256 ;

    /**
     * @param Iterator<TKey, TValue> $iterator
     * @param int-mask-of<self::*> $flags
     */
    public function __construct(Iterator $iterator, int $flags = 0) {}
    /**
     * @return RecursiveCachingIterator<TKey,TValue>
     */
    public function getChildren() {}

    /**
     * @return bool
     */
    public function hasChildren() {}

    /**
     * @return TValue|null current value or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function current() {}

    /**
     * @return TKey|null current key or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function key() {}
}

/**
 * @template TKey
 * @template TValue
 *
 * @template-implements RecursiveIterator<TKey, TValue>
 * @template-extends CallbackFilterIterator<TKey, TValue>
 */
class RecursiveCallbackFilterIterator extends CallbackFilterIterator implements RecursiveIterator {

    /**
     * @param RecursiveIterator<TKey, TValue> $iterator
     * @param callable(TValue, TKey, RecursiveIterator<TKey, TValue>): bool $callback
     */
    public function __construct(RecursiveIterator $iterator, callable $callback) {}
    /**
     * @return RecursiveCallbackFilterIterator<TKey, TValue>
     */
    public function getChildren() {}

    /**
     * @return bool
     */
    public function hasChildren() {}

    /**
     * @return TValue|null current value or null when iterator is drained
     */
    public function current() {}

    /**
     * @return TKey|null current value or null when iterator is drained
     */
    public function key() {}
}

/**
 * @template-implements RecursiveIterator<string, RecursiveDirectoryIterator|string|SplFileInfo>
 * @template-implements SeekableIterator<string, RecursiveDirectoryIterator|string|SplFileInfo>
 */
class RecursiveDirectoryIterator extends FilesystemIterator implements RecursiveIterator, SeekableIterator {

    const CURRENT_AS_PATHNAME = 32 ;
    const CURRENT_AS_FILEINFO = 0 ;
    const CURRENT_AS_SELF = 16 ;
    const CURRENT_MODE_MASK = 240 ;
    const KEY_AS_PATHNAME = 0 ;
    const KEY_AS_FILENAME = 256 ;
    const FOLLOW_SYMLINKS = 512 ;
    const KEY_MODE_MASK = 3840 ;
    const NEW_CURRENT_AND_KEY = 256 ;
    const SKIP_DOTS = 4096 ;
    const UNIX_PATHS = 8192 ;

    /**
     * @param string $path
     * @param int-mask<self::CURRENT_AS_PATHNAME,self::CURRENT_AS_FILEINFO,self::CURRENT_AS_SELF,self::KEY_AS_PATHNAME,self::KEY_AS_FILENAME,self::FOLLOW_SYMLINKS,self::NEW_CURRENT_AND_KEY,self::SKIP_DOTS,self::UNIX_PATHS> $flags
     */
    public function __construct(string $path, int $flags = self::KEY_AS_PATHNAME|self::CURRENT_AS_FILEINFO) {}

    /**
     * @return string
     */
    public function getSubPath() {}
    /**
     * @return string
     */
    public function getSubPathname() {}

    /**
     * @return RecursiveDirectoryIterator|string|SplFileInfo|null current value or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function current() {}

    /**
     * @return string|null current key or null when iterator is drained
     * @psalm-ignore-nullable-return
     */
    public function key() {}
}


/**
 * @template TIterator as RecursiveIterator|IteratorAggregate
 * @mixin TIterator
 */
class RecursiveIteratorIterator implements OuterIterator {
    /**
     * @param TIterator $iterator
     * @param int $mode
     * @param int $flags
     *
     * @return void
     */
    public function __construct($iterator, $mode = 0, $flags = 0) {}
}

/**
 * @template TKey
 * @template TValue
 *
 * @template-implements RecursiveIterator<TKey, TValue>
 * @template-extends RegexIterator<TKey, TValue>
 */
class RecursiveRegexIterator extends RegexIterator implements RecursiveIterator {

    const MATCH = 0 ;
    const GET_MATCH = 1 ;
    const ALL_MATCHES = 2 ;
    const SPLIT = 3 ;
    const REPLACE = 4 ;
    const USE_KEY = 1 ;

    /**
     * @param RecursiveIterator<TKey, TValue> $iterator
     * @param string $regex
     * @param self::MATH|self::GET_MATCH|self::ALL_MATCHES|self::SPLIT|self::REPLACE $mode
     * @param self::USE_KEY|0 $flags
     * @param int $preg_flags
     */
    public function __construct(RecursiveIterator $iterator, string $regex, int $mode = self::MATCH, int $flags = 0, int $preg_flags = 0) {}

    /**
     * @return RecursiveRegexIterator<TKey, TValue>
     */
    public function getChildren() {}
}

/**
 * @template TKey
 * @template TValue
 *
 * @template-extends RecursiveIteratorIterator<TKey, TValue>
 * @template-implements OuterIterator<TKey, TValue>
 */
class RecursiveTreeIterator extends RecursiveIteratorIterator implements OuterIterator {

    const LEAVES_ONLY = 0 ;
    const SELF_FIRST = 1 ;
    const CHILD_FIRST = 2 ;
    const CATCH_GET_CHILD = 16 ;

    const BYPASS_CURRENT = 4 ;
    const BYPASS_KEY = 8 ;
    const PREFIX_LEFT = 0 ;
    const PREFIX_MID_HAS_NEXT = 1 ;
    const PREFIX_MID_LAST = 2 ;
    const PREFIX_END_HAS_NEXT = 3 ;
    const PREFIX_END_LAST = 4 ;
    const PREFIX_RIGHT = 5 ;

    /**
     * @return void
     */
    public function beginChildren() {}

    /**
     * @return RecursiveIterator
     */
    public function beginIteration() {}
    /**
     * @return RecursiveIterator
     */
    public function callGetChildren() {}
    /**
     * @return bool
     */
    public function callHasChildren() {}

    /**
     * @param RecursiveIterator<TKey, TValue>|IteratorAggregate<TKey, TValue> $it
     * @param int-mask<self::BYPASS_CURRENT, self::BYPASS_KEY> $flags
     * @param int-mask<self::CATCH_GET_CHILD> $cit_flags
     * @param self::LEAVES_ONLY|self::SELF_FIRST|self::CHILD_FIRST $mode
     */
    public function __construct($it, int $flags = self::BYPASS_KEY, int $cit_flags = self::CATCH_GET_CHILD, int $mode = self::SELF_FIRST) {}

    /**
     * @return string
     */
    public function current() {}
    /**
     * @return void
     */
    public function endChildren() {}
    /**
     * @return void
     */
    public function endIteration() {}

    /**
     * @return string
     */
    public function getEntry() {}
    /**
     * @return string
     */
    public function getPostfix() {}
    /**
     * @return string
     */
    public function getPrefix() {}
    /**
     * @return string
     */
    public function key() {}
    /**
     * @return void
     */
    public function next() {}
    /**
     * @return void
     */
    public function nextElement() {}
    /**
     * @return void
     */
    public function rewind() {}
    /**
     * @return void
     */
    public function setPostfix(string $postfix ) {}
    /**
     * @param self::PREFIX_* $part
     * @param string $value
     * @return void
     */
    public function setPrefixPart(int $part , string $value ) {}
    /**
     * @return bool
     */
    public function valid() {}
}

/**
 * @template TKey
 * @template TValue
 *
 * @template-extends FilterIterator<TKey, TValue>
 */
class RegexIterator extends FilterIterator {
    const MATCH = 0 ;
    const GET_MATCH = 1 ;
    const ALL_MATCHES = 2 ;
    const SPLIT = 3 ;
    const REPLACE = 4 ;
    const USE_KEY = 1 ;

    /**
     * @param Iterator<TKey, TValue> $iterator
     * @param string $regex
     * @param self::MATCH|self::GET_MATCH|self::ALL_MATCHES|self::SPLIT|self::REPLACE $mode
     * @param int-mask<self::USE_KEY> $flags
     * @param int $preg_flags
     */
    public function __construct(Iterator $iterator, string $regex, int $mode = self::MATCH, int $flags = 0, int $preg_flags = 0) {}
    /**
     * @return TValue Can return any type.
     */
    public function current() {}

    /**
     * @return TKey scalar on success, or null on failure.
     */
    public function key() {}
}