php how to group a multidimensional array by a particular value?

Question

Hopefully, I can explain this correctly...

I have a multidimensional array and am trying to group them according to the value of one the keys.

So, 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

You need to group them by level first

Use foreach to loop into array check if the level is the same with the previous item then group it with that array

  $templevel=0;   

  $newkey=0;

  $grouparr[$templevel]="";

  foreach ($items as $key => $val) {
   if ($templevel==$val['level']){
     $grouparr[$templevel][$newkey]=$val;
   } else {
     $grouparr[$val['level']][$newkey]=$val;
   }
     $newkey++;       
  }
print($grouparr);

---

The output of print($grouparr); will display like the format you hoped for

You can also try to

print($grouparr[7]);

Will display

 [7] => Array (
      [4] => Array (
             [cust] => XT7434
             [type] => standard
             )
      )

Or

print($grouparr[3]);

Will display

[3] => Array (
      [2] => Array (
             [cust] => XT8922
             [type] => premier
             )

      [3] => Array (
             [cust] => XT8816
             [type] => permier
             )
      )

Answer 2

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.