How to group JSON data by the yyyy-mm using date element values?

Question

I have some JSON data that I would like to regroup by months and ultimately put each group into an HTML unordered list with PHP.

The current JSON:

[
   {
        "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
        "date": "2017-03-15"
    },
    {
        "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
        "date": "2017-03-08"
    },
    {
        "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
        "date": "2017-02-25"
    },
    {
        "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
        "date": "2017-02-14"
    },
    {
        "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
        "date": "2016-12-25"
    },
    {
        "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
        "date": "2016-01-06"
    }
]

I think the following structure is what I would need to be able to echo out into the unordered list by month. Please feel free to suggest otherwise.

{
    "2017-03": [
        {
            "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
            "date": "2017-03-15"
        },
        {
            "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
            "date": "2017-03-08"
        }
    ],
    "2017-02": [
        {
            "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
            "date": "2017-02-25"
        },
        {
            "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
            "date": "2017-02-14"
        }
    ],
    "2016-12": [
        {
            "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
            "date": "2016-12-25"
        }
    ],
    "2016-01": [
        {
            "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
            "date": "2016-01-06"
        }
    ]
}

You have unnecessary comma , in json sample data

Yaman Jain
– Yaman Jain

2017-03-17 04:26:26 +00:00
Commented Mar 17, 2017 at 4:26 — Yaman Jain
– Yaman Jain, Commented Mar 17, 2017 at 4:26

Sahil Gulati · Accepted Answer · 2017-03-17 04:14:53Z

1

Hope this will work..

$string='[
    {
        "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
        "date": "2017-03-15"
    },
    {
        "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
        "date": "2017-03-08"
    },
    {
        "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
        "date": "2017-02-25"
    },
    {
        "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
        "date": "2017-02-14"
    },
    {
        "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
        "date": "2016-12-25"
    },
    {
        "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
        "date": "2016-01-06"
    }
]';
$array=array();
$result=array();
$array=  json_decode($string,true);
foreach($array as $value)
{
    $key=explode("-", $value["date"]);
    unset($key[2]);
    $key=implode("-", $key);
    $result[$key][]=$value;
}
echo json_encode($result,JSON_PRETTY_PRINT);

PHP Code demo

answered Mar 17, 2017 at 4:14

Sahil Gulati

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4 Comments

l3fty Over a year ago

This is exactly what I was looking for, thank you. Down votes must be because it was too easy.

Dimi Over a year ago

@l3fty downvotes were because you provided absolutely 0 of your own code, and pretty much asked others to do all the work for you.

l3fty Over a year ago

@Dimi Because I have absolutely no idea how I'd go about doing what I asked. In all honesty, I kept thinking I had to compare dates with the current one and loop through each row. I had thought about posting it but I rather not confused the reader even more with totally incorrect code and just ask a precise question. Isn't that what stackoverflow is for? I didn't see any rules in which I must provide sample code.

Dimi Over a year ago

@l3fty I personally never downvote anything/anyone(still don't have critic badge), but generally speaking any question that does not have any code gets treated like a homework question and therefore ignored by most people. Try to either link some of the things that you have attempted, or paste some broken code.

Yaman Jain · Accepted Answer · 2017-03-17 04:25:41Z

This should help:

<?php
$json = '[{
    "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
    "date": "2017-03-15"
}, {
    "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
    "date": "2017-03-08"
}, {
    "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
    "date": "2017-02-25"
}, {
    "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
    "date": "2017-02-14"
}, {
    "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
    "date": "2016-12-25"
}, {
    "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
    "date": "2016-01-06"
}]';

$json_decode_array = json_decode($json, true);

$result_set = [];

foreach ($json_decode_array as $key => $value) {
    $new_key = explode("-", $value["date"]);
    $result_set_key = $new_key[0] . '-' . $new_key[1];
    $result_set[$result_set_key][] = $value;
}

print_r(json_encode($result_set,JSON_PRETTY_PRINT));

mickmackusa · Accepted Answer · 2017-06-10 16:46:26Z

There will be several ways to do this:

Input:

$json='[
    {"title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
     "date": "2017-03-15"},
    {"title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
     "date": "2017-03-08"},
    {"title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
     "date": "2017-02-25"},
    {"title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
     "date": "2017-02-14"},
    {"title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
     "date": "2016-12-25"},
    {"title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
     "date": "2016-01-06"}
]';

Method: (Demo) a clean and fast foreach loop

$array=json_decode($json,true);
foreach($array as $a){
    $result[substr($a['date'],0,7)][]=$a;  // truncate the dates before assigning as keys
}
echo json_encode($result,JSON_PRETTY_PRINT);

It is utterly silly to explode() the date only to insert the generated elements as the new key, when substr() was specifically designed for substring extraction.

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