How to create associative multidimensional array from input form

I need to create multidimensional array from input form, because I would like pass information to mysql. I created it, but how can I make it associative one? My input:

echo "<input type='number' name='hours_to_save[$my_date][$project[$i]]'/>"

This is how it print now:

array(30) {
    ["2017-05-01"]=>
        array(3) {
            ["kompan"]    => string(1) "2"
            ["5 ogrodow"] => string(1) "3"
            ["karolowo"]  => string(1) "4"
    },
    ...
}

But I would like like this:

array(30) {
  ["2017-05-01"]=>
        array(3) {
            ["project"] => "kompan" , ["hours"] => string(1) "2"

            ["project"] =>"5 ogrodow" , ["hours"] => string(1) "3"

            ["project"] => "karolowo" , ["hours"] => string(1) "4"
    },
    ...
}