Shifting specific index's in array to front based on value inside

Question

I have the following array.

{
  "flow":[
    {
      "tasks":[
        { "id":"1", "uid":"bryan" },
        { "id":"2", "uid":"eric" }
      ]
    },
    {
      "tasks":[
        { "id":"1", "uid":"bryan" },
        { "id":"2", "uid":"eric" }
      ]
    },
    {
      "tasks":[
        { "id":"1", "uid":"bryan" },
        { "id":"2", "uid":"eric" }
      ]
    },
    {
      "tasks":[
        { "id":"1", "uid":"bryan" },
        { "id":"2", "uid":"eric" },
        { "id":"3", "uid":"eric" },
        { "id":"4", "uid":"bryan" }
      ]
    }
  ]
}

Let's say I am eric. If I am eric, I am trying to move all items with the uid of eric to the front of the tasks array.

So that the array would end looking like this:

{
  "flow":[
    {
      "tasks":[
        { "id":"2", "uid":"eric" },
        { "id":"1", "uid":"bryan" }
      ]
    },
    {
      "tasks":[
        { "id":"2", "uid":"eric" },
        { "id":"1", "uid":"bryan" }
      ]
    },
    {
      "tasks":[
        { "id":"2", "uid":"eric" },
        { "id":"1", "uid":"bryan" }
      ]
    },
    {
      "tasks":[
        { "id":"2", "uid":"eric" },
        { "id":"3", "uid":"eric" },
        { "id":"1", "uid":"bryan" },
        { "id":"4", "uid":"bryan" }
      ]
    }
  ]
}

I've attempted to make a function to do it, but for some reason it's not working the way I intended it to. Does anyone know what I'm doing wrong?

function reorder_flow($flow, $uid)
{   
    foreach($flow as &$step)
    {   
        //step is the array with tasks
        $tasks = $step['tasks'];
        $new_tasks = array();

        foreach($tasks as $key => $t)
        {
            if($t['uid'] == $uid)
            {
                $new_tasks = $new_tasks + $t;
                unset($tasks[$key]);
            }
        }
        $step['tasks'] = $new_tasks + $step['tasks'];
    }
    return $flow;
}

In what way is it not working the way you intended? You included what you expect the output to look like, but what does the actual output look like? — jonhopkins
– jonhopkins, Commented Jul 28, 2016 at 18:28
It appears he is outputting it with json_encode @marmeladze — Jeremy Harris
– Jeremy Harris, Commented Jul 28, 2016 at 18:32
As an aside, assuming this is a php array, I'm not 100% sure if using + does what you want, so maybe look into array_merge — jonhopkins
– jonhopkins, Commented Jul 28, 2016 at 18:32

Peter Bailey · Accepted Answer · 2016-07-28 18:45:56Z

This is a traversal/sorting problem.

$json = <<<JSON
{
  "flow":[
    {
      "tasks":[
        { "id":"1", "uid":"bryan" },
        { "id":"2", "uid":"eric" }
      ]
    },
    {
      "tasks":[
        { "id":"1", "uid":"bryan" },
        { "id":"2", "uid":"eric" }
      ]
    },
    {
      "tasks":[
        { "id":"1", "uid":"bryan" },
        { "id":"2", "uid":"eric" }
      ]
    },
    {
      "tasks":[
        { "id":"1", "uid":"bryan" },
        { "id":"2", "uid":"eric" },
        { "id":"3", "uid":"eric" },
        { "id":"4", "uid":"bryan" }
      ]
    }
  ]
}
JSON;

$flow = json_decode($json, true);

array_walk($flow['flow'], function(&$flowItem, $key){
    usort($flowItem['tasks'], function($a, $b){
        $aIsMatch = $a['uid'] === 'eric';
        $bIsMatch = $b['uid'] === 'eric';
        if ($aIsMatch && $bIsMatch) {
            return 0;
        }
        if ($aIsMatch) {
            return -1;
        }
        if ($bIsMatch) {
            return 1;
        }
        // Fallback sorting criteria - you could use something else or just return 0
        return strcasecmp($a['uid'], $b['uid']);
    });
});


echo json_encode($flow, JSON_PRETTY_PRINT);

Ismail RBOUH · Accepted Answer · 2016-07-28 18:46:46Z

1

Please try this:

function sortByUID(&$array, $uid) {

    array_walk ($array, function($obj) use($uid) {
        uasort($obj->tasks, function($a, $b) use($uid)  {
            return $a->uid == $uid ? -1 : 1;
        });
    }); 

}

sortByUID($data->flow, 'eric');

Demo: https://3v4l.org/mOhDX

I hope this will help.

answered Jul 28, 2016 at 18:46

Ismail RBOUH

10.5k2 gold badges26 silver badges37 bronze badges

4 Comments

Peter Bailey Over a year ago

More refined version of what I did - nicely done and I like that you put it in a function

Ismail RBOUH Over a year ago

Yes! only seconds between the 2 answers; We had the same idea ;)

JOUM Over a year ago

I like that version too, fine refactored :)

JOUM Over a year ago

My first editon was like that too, only the array_walk part was the old foreach :)

JOUM · Accepted Answer · 2016-07-28 18:43:24Z

0

notes:

+ does not work with arrays in that way
json_decode should have the second parameter set to true to get nested arrays

then try this in the foreach:

//step is the array with tasks
$new_tasks=array();
foreach($step['tasks'] as $t){
   if($t['uid'] == $uid){
      array_unshift($new_tasks,$t);
   } else {
      array_push($new_tasks,$t);
   }
}

$step['tasks'] = $new_tasks;

edited Jul 28, 2016 at 18:43

answered Jul 28, 2016 at 18:34

JOUM

2542 silver badges3 bronze badges

4 Comments

bryan Over a year ago

Your first answer you posted worked, why did you change it?

JOUM Over a year ago

mmh it worked, ok, then take that, but i think it was not so safty at all. Test some combinations :)

bryan Over a year ago

I appreciate the help! I will try and decipher what's going on here and wrap my head around it :)

JOUM Over a year ago

Late hint: with function () use (&$var) it is possible to inject variables into a function, so that they can used there.

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