如何获取多维数组的最大值30天

Question

I am creating a historical Graph using ChartJS. And I need to Filter the array Values 30 Days Ago

I have an array with the values below:

[0] => Array
    (
        [datetime] => 4/1/2019 4:00:00 PM - 5:00:00 PM
        [value_raw] => 100
    )

[1] => Array
    (
        [datetime] => 4/1/2019 3:00:00 PM - 4:00:00 PM
        [value_raw] => 101
    )

[2] => Array
    (
        [datetime] => 4/1/2019 2:00:00 PM - 3:00:00 PM
        [value_raw] => 99
    )

The Array has large content and contains up to more than 5 months value of every hour every day

This is my current php code as of now for the labels in the ChartJS Script:

LABELS CODE:

labels: [
    <?php
        for($i=0; $i<=30; $i++)
        {
         $label = date('n/d/Y', strtotime('-'.$i.' days',strtotime(date('n/d/Y'))));
         echo '"'.$label.'",';
        }
    ?>
],

Result:

4/01/2019, 3/31/2019, 3/30/2019, 3/29/2019

However I'am having hard time on how am I going to get the equivalent MAX Value per day in parallel to/matching my Labels Code.

DATA CODE:

data: [
    <?php
    foreach ($my_array as $key => $value) {
        for($i=0; $i<=30; $i++)
        {
            $label = date('n/d/Y', strtotime('-'.$i.' days',strtotime(date('n/d/Y'))));

             if ($label == changeFormat($value[datetime]))
             {
                     echo $value['value_raw'].',';
             }
        }
    }
    ?>
],

My Expected Result should be the MAX Value of the Day of the Past 30 Days :

Example:

DATE        VALUE
4/01/2019   99
3/31/2019   101
3/30/2019   100
3/29/2019   95

Result:

99, 101, 100, 95

Answer 1

As the question was about sorting multi-dimesional array based on the key, try this

// remove dates older than 30 days
function remove30DayBeforeDates($a) {
    $pieces = explode(' ', $a['datetime']);
    return strtotime($pieces[0]) > strtotime('-30 days');
}
// remove dates older than 30 days

$array = array(
    array(
        'datetime' => '3/29/2019 4:00:00 PM - 5:00:00 PM',
        'value_raw' => 95
    ), array(
        'datetime' => '4/01/2019 3:00:00 PM - 4:00:00 PM',
        'value_raw' => 99
    ), array(
        'datetime' => '3/31/2019 2:00:00 PM - 3:00:00 PM',
        'value_raw' => 101
    ), array(
        'datetime' => '2/10/2019 2:00:00 PM - 3:00:00 PM',
        'value_raw' => 112
    ), array(
        'datetime' => '3/30/2019 2:00:00 PM - 3:00:00 PM',
        'value_raw' => 100
        ));

$array = array_filter($array, "remove30DayBeforeDates");

// sort array based on the date

function check($a, $b) {
    $pieces1 = explode(' ', $a['datetime']);
    $pieces2 = explode(' ', $b['datetime']);
    return strtotime($pieces2[0]) <=> strtotime($pieces1[0]); // use spaceship operator
}

// sort array based on the date

usort($array, "check");

$value_raw = array_column($array, 'value_raw'); // get array of values from column "value_raw"

print_r(implode(',',$value_raw));