PHP fill an array with missing values

Question

The array below should have a child array for every "point" value from 1 - 7, but 2, 4 and 6 are missing. How can I insert an array for each of those missing values, with a "value" of NULL?

I tried a for($i = 1; $i <= 7; $i++) and inside foreach'ing over my array to see if 'point' == $i or not but that doesn't work.

This is already in a nested foreach of a fairly large array so performance is somewhat important.

Code so far (incomplete and obviously not working)

foreach($measurements as $measurement_id => $set)
        {
            for($i = 1; $i <= 7; $i++)
            {
                foreach($set as $key => $value)
                {
                    $fill = array('value' => null);

                    if($value['point'] == $i)
                        $output[$measurement_id][$key] = $value;
                    else
                        $output[$measurement_id][$key] = $fill;
                }
            }
        }

The array:

            [0] => Array
                (
                    [point] => 1
                    [value] => 1.0
                )

            [1] => Array
                (
                    [point] => 3
                    [value] => 2.0
                )

            [2] => Array
                (
                    [point] => 5
                    [value] => 3.0
                )

            [3] => Array
                (
                    [point] => 7
                    [value] => 4.0
                )

The result should be

             [0] => Array
                (
                    [point] => 1
                    [value] => 1.0
                )

            [1] => Array
                (
                    [point] => 2
                    [value] => NULL
                )

            [2] => Array
                (
                    [point] => 3
                    [value] => 2.0
                )

            [3] => Array
                (
                    [point] => 4
                    [value] => NULL
                )
            [4] => Array
                (
                    [point] => 5
                    [value] => 3.0
                )

            [5] => Array
                (
                    [point] => 6
                    [value] => NULL
                )

            [6] => Array
                (
                    [point] => 7
                    [value] => 4.0

You really want to do this as part of the code for creating the initial array. Where are you getting the data from initially? — Luke
– Luke, Commented Dec 7, 2012 at 17:03

Matteo Tassinari · Accepted Answer · 2012-12-07 17:06:01Z

1

Try this:

$oldArr = [ ..your incomplete array.. ];
$newArr = array();

for ($i = 1; $i < 8; ++$i) {
  $new = array(
    'point' => $i,
    'value' => NULL,
  );

  foreach($oldArr as $old) {
    if ($old['point'] == $i) {
      $new['value'] = $old['value'];
    }
  }

  $newArr[] = $new;
}

now $newArr should contain all the values as you want them.

answered Dec 7, 2012 at 17:06

Matteo Tassinari

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Comments

jeroen · Accepted Answer · 2012-12-07 17:17:14Z

If you original array is ordered by point as in your example, you can do it in one loop only:

$result = array();
for ($i = 1; $i <= 7; $i++)
{
  // get the first element of your set
  $current = reset($set);
  if ($current['point'] === $i)
  {
    // remove the first element of your set and assign it to the result array
    $result[$i - 1] = array_shift($set);
  }
  else
  {
    // create a new, empty entry
    $result[$i - 1] = array('point' => 1, 'value' => NULL);
  }
}

Note that I am creating a new array and removing values from your original one. If you really are worried about resources / performance, you could use the same principle and loop backwards (from 7 to 1), moving the last element of your array to the correct position and filling the empty spaces the same way.

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