Jumping to an array key

I had just posted a thread on inbuilt iterator classes. W/o using an iterator class… is there a way move the array pointer to a specific value?

For example lets say I had an array with 1000+ items! I know I dont need to search through the first 550. is there a way to set the pointer to the 550th item and start the loop there?

BTW, I know a foreach resets the counter, but I am not sure if a while loop would work…

All input, as always, greatly appreciated.

Are the keys numerical?

yes numerical keys, but they may or may not be sequential…

This post on stack seemed to specify some things, one being you can not modify the pointer, but you can use key/next:

Ok, but it just seems like, if you had a large array, to go trough a percentage of the loop simply to REACH the part of the array you want to work with would be a somewhat inefficient use of computer power…

I mean, you wouldn’t necessarily have to use a foreach loop to cycle through the array starting at 550.

for ($i=550; $i<count($array); $i++)
     $array[$i] = "550th key.";

Or maybe even something like:

for ($i=(count($array)/2); $i<count($array); $i++)
echo $array[$i]; // In an array of 10 items, this would be the 5th!

That code might not work verbatim, but you get the logic.

ah, I think I understand… so the key (no pun) is not to rely on foreach?

Although there is one caveat to to your method. That is if the array is non sequential… $arr[1], $arr[3], $arr[5],$arr[7],$arr[10,$arr[12],$arr[15]…

$a = array(

$parts = array_chunk($a, 5, 1);

var_dump ($parts[1]);

//  2 => string 'France' (length=6)
//  3 => string 'Germany' (length=7)
//  4 => string 'France' (length=6)
//  5 => string 'France' (length=6)

array_chunk( your array, size to split into, [BOOL preserve keys]);

In the above case, if you wanted to split the first 3 results you would have to join the remaining arrays back together again in order to have a new array without the first 3.

Would that work?


Actually, array_slice might be better

$output = array_slice($a, 3, null, true);     

var_dump( $output );

//  8 => string 'England' (length=7)
//  9 => string 'England' (length=7)
//  2 => string 'France' (length=6)
//  3 => string 'Germany' (length=7)
//  4 => string 'France' (length=6)
//  5 => string 'France' (length=6)

function seek(array & $array, $key){
    if($key === key($array)){
      return true;
  return false;

$array = range(0, 100);

seek($array, 56);

echo current($array); #56

So I take it the only way to move the array pointer is one key at a time?

incidentally… for seeking a particular key array , I came up with the following method. The only problem is it doesn’t actually move the pointer unless I add a loop…

function seek($arr, $order){
return $arr[$kmap[$order]];

I suppose I will have to stick to loops. It would be have been nice tho, if you could START an iteration or use each() at a specific point in the array (as oppose to walking up from 0)

With regards to seeking to an offset (not a key), there was some discussion about adding such a function on the PHP internals mailing list ([PHP-DEV] array_seek function) but nothing came of it.

My opinion for this thread is that you’re doing it wrong. If you only want to iterate over a part of the array, is there any reason that you can think of as to why you cannot make a new array containing only the items that you are interested in. array_slice() is fine for that. Of course there are other options like using a LimitIterator on an ArrayIterator, or wrestling with for/while/etc. loops.

Thanks Salathe,

It’s a shame this was never added, maybe in my naivety, I think a seek function to move the internal pointer would be an essential part of the standard tool-kit.

PHP has obviously done quite well without it, but it just seems natural to have to this.

I also agree with the point you made on the internal mailing list, a ‘truthy’ seek function would be more suited.

Hope you’re well.


no reason… now that i think of it other than the extra use of memory. :slight_smile: