Array question

If I have an array like this > [0] => 1 [1] => 2 [2] => 3 ... [99] => 100 If I want to select [50] => 51 and store the value that's 2 positions before and 1 position after, how can I do? If I want to know what position value 71 have? I have search the PHP-manual and found some functions as prev, next, pos etc. But with these commands I have to loop thru the array every time to reach the the values and positions. It has to be an easier way to do it. // jocke