Variable assignment resets internal array pointer

Question

I have this PHP code:

$a=array(1, 2, 3);
var_dump(current($a));
each($a);
each($a);
each($a);
var_dump(current($a));
$b=$a;
var_dump(current($a));

The output is "int(1) bool(false) int(1)" but I expect "int(1) bool(false) bool(false)", because after three times each the internal pointer of $a should be after the end of the array and stay there.

But apparently the assignment $b=$a sets the pointer of $a back to the first element again. What is going on here?

(If I remove one each, the output is "int(1) int(3) int(3)" as expected.)

your question is bit unclear. sorry may be i am unable, but still can you put your expected outcome in a bit nicer way? — Death-is-the-real-truth
– Death-is-the-real-truth, Commented Feb 6, 2016 at 23:41

Gavriel · Accepted Answer · 2016-02-06 23:45:14Z

2

From http://php.net/manual/en/function.each.php:

Caution: Because assigning an array to another variable resets the original array's pointer, our example above would cause an endless loop had we assigned $fruit to another variable inside the loop.

answered Feb 6, 2016 at 23:45

Gavriel

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7 Comments

Wolfgang Stengel Over a year ago

Why does the assignment not reset the pointer if there are only two each instead of three?

Gavriel Over a year ago

That's a good question, and I guess the answer is in the question :) I guess it only resets when it got to the end. Open a bug-report to php so they fix clarify it in the documentation...

Terry Seidler Over a year ago

In PHP7 this does what you'd expect (return 1, false, false) according to sandbox.onlinephpfunctions.com.... In 5.6 it seems it doesn't...

Wolfgang Stengel Over a year ago

Right... sounds like this was some sort of side effect which got fixed in PHP 7. Thank you both.

Gavriel Over a year ago

Well "fixed" is probably depending on point of view, I would say "changed the undocumented behavior", which of course will break some working code for people when upgrading php :)

|

cFreed · Accepted Answer · 2016-02-06 23:47:39Z

1

It's by design. This PHP manual page states:

Caution Because assigning an array to another variable resets the original array's pointer, our example above would cause an endless loop had we assigned $fruit to another variable inside the loop.

answered Feb 6, 2016 at 23:47

cFreed

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Comments

Konstantin Yaniv · Accepted Answer · 2016-07-05 07:31:39Z

1

This behavior is corrected in PHP 7.

$a=array(1, 2, 3);
var_dump(current($a)); // 1
each($a);
each($a);
each($a);
var_dump(current($a)); // false
$b=$a;
var_dump(current($a)); // php7-> false; php5.6 -> 1

The changes described on php wiki page.

answered Jul 5, 2016 at 7:31

Konstantin Yaniv

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