display dates from an array in json in descending order in php

Question

I have a JSON file, where there are dates, but I want to sort them in descending order when they go through a foreach.

{
    "posts": [
        {
            "id": "50",
            "name": "Charlotte Johnson",
            "date": "2021-02-08 10:15:38"
        },
        {
            "id": "51",
            "name": "Emma Jones",
            "date": "2021-02-09 18:30:38"
        },
        {
            "id": "52",
            "name": "Benjamin Miller",
            "date": "2021-02-10 23:47:38"
        }
    ]
}

I loop through the data from the JSON file. I use usort but the dates are still not showing descending.

<?php
    $datajson = json_decode(file_get_contents("results.json"));

    usort($datajson->posts, function($a, $b) {
       return strtotime($a->date) - strtotime($b->date);
    });

    foreach($datajson->posts as $row)
        {
            $date = date('Y-m-d H:i:s', strtotime($row->date));
            echo " Date: ". $date ."<br />";
        }
?>

the dates that the PHP shows me

Date: 2021-02-08 10:15:38
Date: 2021-02-09 18:30:38
Date: 2021-02-10 24:47:38

but I want to sort them in descending order and display them like this

Date: 2021-02-10 24:47:38
Date: 2021-02-09 18:30:38
Date: 2021-02-08 10:15:38

Can you help me with this query?

For descending, just reverse the parameters inside the callback $b - $a. — El_Vanja
– El_Vanja, Commented Feb 10, 2021 at 18:38
Also, not a sort issue, but this doesn't seem to be needed $date = date('Y-m-d H:i:s', strtotime($row->date)); — AbraCadaver
– AbraCadaver, Commented Feb 10, 2021 at 18:41
Thanks to both of you for indicate what the problem was. I already removed the line from the $ date. — Alonso Benites
– Alonso Benites, Commented Feb 10, 2021 at 19:05

dev_mustafa · Accepted Answer · 2021-02-10 18:49:45Z

1

You need to reverse the function parameters.

usort($datajson->posts, function($a, $b) {
         return strtotime($b->date) - strtotime($a->date) ;
     });

Here is result output

answered Feb 10, 2021 at 18:49

dev_mustafa

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1 Comment

Alonso Benites Over a year ago

Thanks, I already modified and it worked.

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