Question

Say I have an array that looks like this:

array(100) {
  [0]=>
  array(4) {
    ["player_id"]=>
    string(2) "jk"
    ["date"]=>
    string(10) "2012-11-07"
    ["hits"]=>
    string(4) "1000"
  }
  [1]=>
  array(4) {
    ["player_id"]=>
    string(2) "jk"
    ["date"]=>
    string(10) "2012-11-14"
    ["hits"]=>
    string(4) "2000"
  }
 [2]=>
  array(4) {
    ["player_id"]=>
    string(2) "mc"
    ["date"]=>
    string(10) "2012-11-14"
    ["hits"]=>
    string(4) "1500"
  }
 [3]=>
  array(4) {
    ["player_id"]=>
    string(2) "mc"
    ["date"]=>
    string(10) "2012-11-07"
    ["hits"]=>
    string(4) "2300"
  }

…

And this continues. So, basically I have several players and for each player I have two dates. I would like to end up having an array like this:

array(100) {
      ["jk"]=>
      array(2) {
        ["hits_today"]=>
        string(4) "1000"
        ["hits_difference"]=>
        string(5) "-1000"
      }
     ["mc"]=>
      array(2) {
        ["hits_today"]=>
        string(4) "1500"
        ["hits_difference"]=>
        string(4) "-800"
      }
    ..

Basically I want to process the first array knowing that for each player I (might) have two values, and create an array of arrays that as keys uses the player_id and as components with the difference between those two values, and the value of today.

My concerns are:

• What is the best way to process the first array?
• How would I manage if the value of today doesn’t exist, or the value of tomorrow doesn’t? How can I control that while processing the array?

Answer 1

If this comes from a query I would do this instead:

SELECT player_id,
SUM(IF(`date`='$yesterday', hits, 0)) AS hits_yesterday,
SUM(IF(`date`='$today', hits, 0)) AS hits_today
FROM ...
GROUP BY player_id