How to sort a JSON array with PHP

Question

First of all i'm a complete newbie to this, i have searched for solutions but none seem to do the trick.

So I am trying to sort this JSON array by date but i don't really know i should tackle this, any tips in the right direction are much appreciated!

["info":[
{"id":1, "title":"original title", "name":"john doe", "date":"2010-05-15"}, 
{"id":2, "title":"another title", "name":"foo bar", "date":"2009-04-11"},
...

So i'm getting the data like this

$data=file_get_contents('jsondata...');
$d=json_decode($data,true);

I would like to sort the data by date, any ideas how i should approach this? Is it also possible to return the year value only? So the output would be 2009 instead of 2009-04-11?

Thanks in advance

Solution

You can use usort and a custom comparison function:

$data = '{"info":[{"id":1, "title":"original title", "name":"john doe", "date":"2010-05-15"}, {"id":2, "title":"another title", "name":"foo bar", "date":"2009-04-11"}]}';

$info = json_decode($data, true)['info'];

usort($info, function ($a, $b) {
    return $a['date'] <=> $b['date'];
});

<=> works on strings here because a string comparison is also a date comparison when your dates are formatted as YYYY-MM-DD.

Then, to show the year value for an entry, you can parse the date into a DateTime and reformat it:

$date = DateTime::createFromFormat('Y-m-d', $item['date']);
$year = $date->format('Y');

Here's a demo.

Comments

[Ry-]

You also don't need uasort because the keys are numeric, and ordering them maintaining the numeric keys can be incredibly confusing (in your output, 0 comes after 1).

[cypher]

Yes, it does and does so because I want it to. I don't want to modify the array any more then it's necessary for no reason. What if the key is actually important?

[Ry-]

I'll bet you $50 that the OP does not want item 1 to come before item 0 in the array, especially since it wasn't associative to begin with ;)

[cypher]

You can bet me whatever you want, I'm not changing indexes just because I think that I can.

[Ry-]

Sigh I don't think you understand how ridiculous having an array in that order with those keys is. But whatever.

[cypher]

Does it sound more riddiculous then relying on "1 comes after 0"? That can get even more confusing.

[Ry-]

Yes, it does. I'm sorry, but look - you're arguing that relying on 1 coming after 0 is ridiculous. 1 comes after 0. It's not confusing, it's math.

[cypher]

Math has nothing to do with it, we're talking about a hash map (yes, in PHP, array is an ordered hash map). In hash map, the key has no ordering meaning. Let's make a pros and cons list: + Both functions order an array. - With usort, you reindex the array for no valid reason. Now what would confuse me? I'll do echo $array[0]; //prints Foo usort($array); echo $array[0]; //prints Bar Of course, there's a case when I want to get the first element. Wait, that should be done with reset. I see no reason for changing indexes when I don't need to.

[xtoffer]

Thank you so much for this, got it working now! Thanks for your effort to explain this! I really appreciate it

[xtoffer]

Thank you for your feedback andreas i really appreciate it

[Laci]

@xtoffer You should accept an answer as correct so you don't just appreciate their effort to help you, but you can also help someone like me who has the same issue as you and I try to find out which answer from here is the correct one! Thank you in advance!

[joshuahedlund]

Note: As of PHP 5.2.2, DateTime objects can be compared using comparison operators, so you should just be able to return ($dA > $dB)

[Ry-]

@joshuahedlund: usort doesn’t expect a boolean return, but you’re right, it doesn’t make much sense to compare only the year even if you only show the year.

[user982853]

Does this work on large lists? or just lists of two?

[AbraCadaver]

No need to convert if they're in this format 2010-05-15