Was ist ein Iterator in PHP?

    //抽象聚合类
    abstract class Aggregate
    { 
        public abstract Iterator CreateIterator();
    }    
    //具体聚合类
    class ConcreteAggregate : Aggregate
    {        
        private IList<object> items = new List<object>();        
        public override Iterator CreateIterator()
            {            
                return new ConcreteIterator(this);
            }        
        public int Count
        {            
            get { 
            return items.Count; 
            }
        }        
        public object this[int index]
        {            
            get { return items[index]; }            
            set { items.Insert(index, value); }
        }
    }    
    //抽象迭代器类
    abstract class Iterator
    {        
        public abstract object First();        
        public abstract object Next();        
      public abstract bool IsDone();        
      public abstract object CurrentItem();
    }     
    //具体迭代器类
    class ConcreteIterator : Iterator
    {        
        private ConcreteAggregate aggregate;        
        private int Current = 0;        
        public ConcreteIterator(ConcreteAggregate aggregate)
        {            
        this.aggregate = aggregate;
        }        
        public override object CurrentItem()
        {            
            return aggregate[Current];
        }        
        public override object First()
        {            
            return aggregate[0];
        }        
        public override bool IsDone()
        {            
            return Current >= aggregate.Count ? true : false;
        }        
        public override object Next()
        {            
                object ret = null;
            Current++;            
            if(Current<aggregate.Count)
            {
                ret = aggregate[Current];
            }            
            return ret;
        }
    }     
    static void Main(string[] args)
        {
            ConcreteAggregate aggregate = new ConcreteAggregate();
            aggregate[0] = "michael";
            aggregate[1] = "jarle";
            aggregate[2] = "cumming";
            aggregate[3] = "andy";
            ConcreteIterator iterator = new ConcreteIterator(aggregate);
            iterator.First();            while (!iterator.IsDone())
            {
                Console.WriteLine($"{iterator.CurrentItem()},请打卡后再下班");
                iterator.Next();
            }
            Console.Read();
        }