# Sorting a multidimensional array in PHP

I was developing a simple web service to retrieve data from a data server and I want to sort the result by the key’s value of a sub-array.

I’m talking about an array who looks like this:

```
Array
(
[0] => Array
(
[k] => 15
[Outlayer] =>
[ClusMethod] => mds kmeans
[MaxCluser] => 10
)
[1] => Array
(
[k] => 6
[Outlayer] =>
[ClusMethod] => mds kmeans
[MaxCluser] => 5
)
[2] => Array
(
[k] => 6
[Outlayer] => 1
[ClusMethod] => mds kmeans
[MaxCluser] => 5
)
[3] => Array
(
[k] => 9
[Outlayer] => 1
[ClusMethod] => mds kmeans
[MaxCluser] => 7
)
```

)

I want to order the array using `k`

value of each inner array and then by `Outlayer`

. PHP provides some functions for sorting arrays ( like `asort()`

or `ksosrt()`

) but I haven’t found anyone useful for this case. So I develop my own functions to order this type of arrays.

The goal of first function is to order a array by a specified key of its inners arrays:

```
function sort_array_by_key($arr, $key) {
$keys = array();
foreach ($arr as $k => $value) {
$keys[$k] = strtolower($value[$key]);
}
asort($keys);
$result = array();
foreach ($keys as $k => $value) {
$result[] = $arr[$k];
}
return $result;
}
```

An example of its output, ordering my array by `k`

value:

```
Array
(
[0] => Array
(
[k] => 6
[Outlayer] => 1
[ClusMethod] => mds kmeans
[MaxCluser] => 5
)
[1] => Array
(
[k] => 6
[Outlayer] =>
[ClusMethod] => mds kmeans
[MaxCluser] => 5
)
[2] => Array
(
[k] => 9
[Outlayer] => 1
[ClusMethod] => mds kmeans
[MaxCluser] => 7
)
[3] => Array
(
[k] => 15
[Outlayer] =>
[ClusMethod] => mds kmeans
[MaxCluser] => 10
)
)
```

So, now, I have a multidimensional array sorted by one of its inner keys. But the goal is to be able to sort by anyone of its inner keys, also by more than one. I archive this goal developing the following function:

```
function sort_array_by_keys($arr, $arrkey) {
$keys = array();
foreach ($arr as $k1 => $value1) {
$keys[$k1] = array();
foreach ($arrkey as $k2 => $value2) {
$keys[$k1][] = strtolower($value1[$value2]);
}
}
asort($keys);
$result = array();
foreach ($keys as $k => $value) {
$result[] = $arr[$k];
}
return $result;
}
```

And this is what I was expecting to see:

```
Array
(
[0] => Array
(
[k] => 6
[Outlayer] =>
[ClusMethod] => mds kmeans
[MaxCluser] => 5
)
[1] => Array
(
[k] => 6
[Outlayer] => 1
[ClusMethod] => mds kmeans
[MaxCluser] => 5
)
[2] => Array
(
[k] => 9
[Outlayer] => 1
[ClusMethod] => mds kmeans
[MaxCluser] => 7
)
[3] => Array
(
[k] => 15
[Outlayer] =>
[ClusMethod] => mds kmeans
[MaxCluser] => 10
)
)
```