Why PHP keeps resetting the array pointer?

Question

So I spent 2 hours trying to figure this out, minimizing the code as much as possible to isolate the problem, yet I can't figure this out.

So I have this code:

$arr['key']['name'] = array("one", "two", "three");

$counter = 0;
do
{
    $cur = current($arr);

    $k = key($arr['key']['name']);
    next($arr['key']['name']);
}while($k !== null);

This is a never ending loop. For some reason, after going through all the $arr['key']['name'] values, key() instead of returning NULL, goes back to 0 again. Removing $cur = current($arr); however solves that problem. According to php manual, current() doesn't affect the array pointer at all. Now I know that copying an array will reset its pointer but there's no copying going on and if there was $k would constantly be zero instead of going from 0 to 2 and then resetting back to 0.

You'd need $cur = current($arr['key']['name']); if you're doing next($arr['key']['name']);. — nickb
– nickb, Commented Apr 10, 2012 at 4:53
Because then I would get the current element of $arr['key']['name'] instead of a the current element of $arr which is $arr['key'] :) — John
– John, Commented Apr 10, 2012 at 4:57
This seems like something undocumented/bug. I rewrote "$cur = current($arr);" to "current($arr);" and the loop ended all right. Or I replaced "$arr['key']['name']" with "$arr['name']" and the loop ended all right. — Jānis Elmeris
– Jānis Elmeris, Commented Oct 14, 2013 at 15:53

Ignacio Vazquez-Abrams · Accepted Answer · 2012-04-10 04:55:38Z

4

current() doesn't move the array pointer for the array you use it on, but you're using it on different arrays. It is resetting the pointer for the nested arrays.

answered Apr 10, 2012 at 4:55

Ignacio Vazquez-Abrams

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3 Comments

John Over a year ago

How come? It doesn't make sense and it isn't mentioned anywhere in the current()'s manual.

Ignacio Vazquez-Abrams Over a year ago

Probably because no one ever expected it to be used this way.

John Over a year ago

Yes but if it really does reset the pointer for the nested arrays, why doesn't it do so on every iteration when current() runs but only after the whole $arr['key']['name'] array has been traversed?

Dr.Kameleon · Accepted Answer · 2012-04-10 04:54:01Z

2

Why don't you do it this way ?

Code :

foreach ($arr['key']['name'] as $k)
{
    // do something with $k

}

answered Apr 10, 2012 at 4:54

Dr.Kameleon

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1 Comment

John Over a year ago

Because I don't need to access all the elements at one run, I just made that small example to demonstrate the problem, in my real code it is not a loop :)

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