How to set an Arrays internal pointer to a specific position? PHP/XML

If your array is always indexed consistently (eg. 'page1' is always at index '0'), it's fairly simple:

$List = array('page1', 'page2', 'page3', 'page4', 'page5');
$CurrentPage = 3; // 'page4'

while (key($List) !== $CurrentPage) next($List); // Advance until there's a match

I personally don't rely on automatic indexing because there's always a chance that the automatic index might change. You should consider explicitly defining the keys:

$List = array(
    '1' => 'page1',
    '2' => 'page2',
    '3' => 'page3',
);

EDIT: If you want to test the values of the array (instead of the keys), use current():

while (current($List) !== $CurrentPage) next($List);

Using the functions below, you can get the next and previous values of the array. If current value is not valid or it is the last (first - for prev) value in the array, then:

• the function getNextVal(...) returns the first element value
• the function getPrevVal(...) returns the last element value

The functions are cyclic.

function getNextVal(&$array, $curr_val)
{
    $next = 0;
    reset($array);

    do
    {
        $tmp_val = current($array);
        $res = next($array);
    } while ( ($tmp_val != $curr_val) && $res );

    if( $res )
    {
        $next = current($array);
    }

    return $next;
}

function getPrevVal(&$array, $curr_val)
{
    end($array);
    $prev = current($array);

    do
    {
        $tmp_val = current($array);
        $res = prev($array);
    } while ( ($tmp_val != $curr_val) && $res );

    if( $res )
    {
        $prev = current($array);
    }

    return $prev;
}

Using the functions below, you can get the next and previous KEYs of the array. If current key is not valid or it is the last (first - for prev) key in the array, then:

• the function getNext(...) returns 0 (the first element key)
• the function getPrev(...) returns the key of the last array element

The functions are cyclic.

function getNext(&$array, $curr_key)
{
    $next = 0;
    reset($array);

    do
    {
        $tmp_key = key($array);
        $res = next($array);
    } while ( ($tmp_key != $curr_key) && $res );

    if( $res )
    {
        $next = key($array);
    }

    return $next;
}

function getPrev(&$array, $curr_key)
{
    end($array);
    $prev = key($array);

    do
    {
        $tmp_key = key($array);
        $res = prev($array);
    } while ( ($tmp_key != $curr_key) && $res );

    if( $res )
    {
        $prev = key($array);
    }

    return $prev;
}