How to group a multidimensional array by a particular subarray value?

Question

I have a multidimensional array and am trying to group them according to the value in a specific column.

I'm trying to group them by level, but I won't actually know the level beforehand. So, it's not like I can put it in a for loop and say while $i < 7, because I won't know that 7 is the maximum value for the level key, and frankly, I'm not sure that's how I would need to do it even if I did...

Array (    [0] => Array (           [cust] => XT8900           [type] => standard           [level] => 1           )    [1] => Array (           [cust] => XT8944           [type] => standard           [level] => 1           )    [2] => Array (           [cust] => XT8922           [type] => premier           [level] => 3           )    [3] => Array (           [cust] => XT8816           [type] => permier           [level] => 3           )    [4] => Array (           [cust] => XT7434           [type] => standard           [level] => 7           ) ) 

What I'm hoping to produce:

Array (     [1] => Array (           [0] => Array (                     [cust] => XT8900                     [type] => standard                     )           [1] => Array (                     [cust] => XT8944                     [type] => standard                     )           )     [3] => Array (           [2] => Array (                  [cust] => XT8922                  [type] => premier                  )            [3] => Array (                  [cust] => XT8816                  [type] => permier                  )           )     [7] => Array (           [4] => Array (                  [cust] => XT7434                  [type] => standard                  )           ) ) 

Answer 1

Best way, if you have control over building the initial array, is just set things up like that at the start as you add entries.

If not then build a temporary array to sort:

foreach ($input_arr as $key => &$entry) {     $level_arr[$entry['level']][$key] = $entry; } 

Leaves you with the form you wanted and everything referenced together.

Build the array like that in the first place though if at all possible.