php - Apply column min and column max to every row in a 2d array

Solution:

This will help -

$data=array(array("day1"=>1,"day2"=>1,"name"=>"Ram"),array("day1"=>1,"day2"=>2,"name"=>"Raj"),array("day1"=>1,"day2"=>3,"name"=>"Rahul"),array("day1"=>2,"day2"=>3,"name"=>"Rocky"));
// Get all values for day1 & day2 and store them in one array
$values = array_merge(array_column($data, 'day2'), array_column($data, 'day1'));
// Assign values
$data = array_map(function($d) use($values) {
    // Assign the minimum value
    $d['day1'] = min($values);
    // assign the maximum value
    $d['day2'] = max($values);
    return $d;
}, $data);

echo json_encode($data);
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Output

[{"day1":1,"day2":3,"name":"Ram"},{"day1":1,"day2":3,"name":"Raj"},{"day1":1,"day2":3,"name":"Rahul"},{"day1":1,"day2":3,"name":"Rocky"}]
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Solution:

this will help: check the demo

    $data=array(array("day1"=>1,"day2"=>1,"name"=>"Ram"),array("day1"=>1,"day2"=>2,"name"=>"Raj"),array("day1"=>1,"day2"=>3,"name"=>"Rahul"),array("day1"=>2,"day2"=>3,"name"=>"Rocky"));
    $min = min(array_column($data, 'day1'));
    $max = max(array_column($data, 'day2'));
    $result = array_map(function($v) use($min, $max){$v['day1'] = $min; $v['day2'] = $max; return $v; }, $data);
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Solution:

Instead of using multiple cycles (foreach() loops and orarray_column() calls), this task can be completed in 1 cycle by declaring reference variables at all elements which need to be updated with the min/max values.

Below, the final iteration's$day1 and$day2 values will be distributed to all points of reference.

Code: (Demo)

foreach ($array as &$row) {
    $day1 = min($day1 ?? $row['day1'], $row['day1']);
    $day2 = max($day2 ?? $row['day2'], $row['day2']);
    $row['day1'] = &$day1;
    $row['day2'] = &$day2;
}
var_export($array);
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