在Iterator（php）中使用密钥的任何方法？

Question

I have created a php class that implements the Iterator interface. I am successfully able to iterate through the class like this:

foreach($data as $key=>$value)
    echo $key;

This, however, consistently gives me a strange result:

foreach($data as $item)
    echo key($item)

The first style calls the key() method in my class for every element. The latter never calls it.

Am I missing something? That should work, shouldn't it?

Update: I think I am missing something. The key function doesn't work as I would expect it to for a simple array, either:

$test = [['name'=>'foo'],['name'=>'bar'],['name'=>'fizz']];

foreach($test as $key=>$item)
    echo $key;

foreach ($test as $item)
    echo key($item);

gives me 012namenamename... not quite what I was expecting. I think I need to just use the $key=>value notation, and never count on key() in a loop.

Answer 1

Your first version is correct, which is why it works. For a short explanation of why your second method doesn't work, see this comment in the manual.

This is because (from the manual for foreach() )

On each iteration, the value of the current element is assigned to $value and the internal array pointer is advanced by one

So your second method is fetching the next key, not the current one.