Manipulation of an array

[yoda69]

Hey all,
I'm using an array to populate labels for a graph. When I have a lot of keys in the array (user answered a questionnaire many times) there are too many labels in graph and it does not look good.
I want to limit the number of key in the array to 15.
Do you have any ideas about good ways to manipulate the array but leaving the 1'st and last values, and choosing interval keys between them?

Or do you think it will be simpler to do this on mysql level?
Thanks,

[Weedpacket]

PHP has a lot of functions for working with arrays; [man]array_slice[/man] is the first that comes to mind, followed by [man]array_chunk[/man]. [man]reset[/man] and [man]end[/man] also give the first and last elements of an array. There's also a trick mentioned in the user notes on [man]array_map[/man] that can come in handy.

To get every fifth element of an array, as well as the first and last elements

$first_element = reset($array);
$last_element = end($array);
$array_sections = array_chunk($array, 5);
// Transpose (see user notes in array_map)
$array_sections = array_unshift($array_sections, null);
$array_sections = call_user_func_array('array_map', $array_sections);
// Just the first elements of each section
$sampled_array = array_map('reset', $array_sections);
// We already have the first element - don't want to repeat it
array_shift($sampled_array);
// We don't want to repeat the last element either.
if(count($array) % 5 == 1)
{
    array_pop($sampled_array);
}
array_unshift($sampled_array, $first_element);
array_push($sampled_array, $last_element);

(Note: totally untested.)