使用嵌套数组创建唯一键并计数值

Question

In PHP I want to construct an array that uses the distinct $raw['day'] as each row, and count up all the $raw['delay'] that are greater than 0:

Start

$raw = array(
  [0] => ("day" => "2013-01-01", "delay" => 3),
  [1] => ("day" => "2013-01-01", "delay" => 16),
  [2] => ("day" => "2013-01-01", "delay" => 0),
  [3] => ("day" => "2013-01-02", "delay" => 1),
  [4] => ("day" => "2013-01-02", "delay" => 0),
  [5] => ("day" => "2013-01-03", "delay" => 9),
);

Result

array(
  [0] => ("day" => "2013-01-01", "misses" => 2),
  [1] => ("day" => "2013-01-02", "misses" => 1),
  [2] => ("day" => "2013-01-02", "misses" => 1),
)

What I've tried:

I was thinking first I'd get all unique days:

$all_days = array_column($raw, 'day');
$unique_days = array_unique($all_days);

Now that I've got all unique days, I can loop through $raw again and increment the misses. But this seems overly verbose, and I figured among PHP's array functions there would be an easier solution.

foreach ($raw as $row) {
  if ($row['delay'] > 0) {
    $unique_days[$row['day']]++
  }
}

Answer 1

you can use array_walk function, but I suppose the only thing you need is:

    $unique_days = array();
    foreach ($raw as $row) {
if (!isset($unique_days[$row['day']])) $unique_days[$row['day']] = 0; -- place 1
      if ($row['delay'] > 0) {
if (!isset($unique_days[$row['day']])) $unique_days[$row['day']] = 0; -- place 2
        $unique_days[$row['day']]++
      }
    }

it will store only unique days with proper counter

UPDATE check places 1 and 2 - first one is needed if you need all days in final array, second is needed if you need only unique days and don't want warning

Answer 2

This is one possible approach:

$sum=array();
foreach ($raw as $r) {
    if ($r["delay"]>0) $sum[$r["day"]]++;
}

and then

foreach ($a as $k => $v) {
 $sum[]=array("day"=>$k, "misses" => $v);
}
print_r($sum);

Test

$raw = array(
  0 => array("day" => "2013-01-01", "delay" => 3),
  1 => array("day" => "2013-01-01", "delay" => 16),
  2 => array("day" => "2013-01-01", "delay" => 0),
  3 => array("day" => "2013-01-02", "delay" => 1),
  4 => array("day" => "2013-01-02", "delay" => 0),
  5 => array("day" => "2013-01-03", "delay" => 9),
);
$a=array();
foreach ($raw as $r) {
    if ($r["delay"]>0) {$a[$r["day"]]++;}
}

foreach ($a as $k => $v) {
print "$k = $v<br>";
}

foreach ($a as $k => $v) {
 $sum[]=array("day"=>$k, "misses" => $v);
}
print_r($sum);

Returns

Array (
 [0] => Array ( [day] => 2013-01-01 [misses] => 2 )
 [1] => Array ( [day] => 2013-01-02 [misses] => 1 )
 [2] => Array ( [day] => 2013-01-03 [misses] => 1 ) )