foreach and current - php

Question

<?php
$a = array(1, 2, 3, 4, 5);
foreach ($a as $key => $elem) {
echo "$key = $elem"; echo ' = ';
var_dump(current($a));\
}
?>
The output I get when running that is as follows:
0 = 1 = int(2)
1 = 2 = int(2)
2 = 3 = int(2)
3 = 4 = int(2)
4 = 5 = int(2)
Seems to me that this is the output I should be getting?:
0 = 1 = int(1)
1 = 2 = int(2)
2 = 3 = int(3)
3 = 4 = int(4)
4 = 5 = int(5)
I do current() before the for loop on $a and get int(1). Thus it seems like it's the foreach loop that's causing it to increment. But if that's the case why is it only doing it once?
If I call next() in the for loop it increments but not otherwise. Of course next() starts out at int(3) (ie. the value after int(2))..

Answer 1

From reading the PHP documention on current, it does not look like you should expect foreach to move the current pointer.
Please see:
http://php.net/manual/en/function.current.php
What's a bit confusing is that the each function does move the current pointer. So if you rewrite your array as a loop using each rather than foreach, then you will get the desired current behavior.
Here's your example rewritten with each(), which produces the expected results:
<?php
$a = array(1, 2, 3, 4, 5);
while ( list($key,$elem) = each($a)) {
echo "$key = $elem"; echo ' = ';
var_dump(current($a));
}
?>

Answer 2

current() uses the internal flag (pointer) and foreach uses it's own.
If you want to do this (which is kind of silly as you have the key in $key) you can use ArrayIterator

Answer 3

I just stumbled on the same problem, and I believe I have a theory.
Foreach doesn't access the array elements by value, it creates its own copy. However, while doing this, it increments the value returned by current() just once.
To check this:
<?php
$a = [0, 1, 2];
foreach ($a as &$val){ // accessing the array elts by reference this time
var_dump(current($a));
}
/*this outputs:
int(1)
int(2)
bool(false)*/