Sorting associative array with multiple conditions

Question

I have a table called "parents_kids", it has three columns known as:

id  Guardian    kids
1   Greg        1
2   Gary        3
3   Aaron       2
4   Farb        3
5   REX         1
6   Fred        2

In the following code I get it into array and print it:

$exc = $conn->prepare("SELECT ID,Guardian,kids from current_state");
        $exc->execute();
            while($finalResult = $exc->fetch(PDO::FETCH_ASSOC))
             {
                        $tables[] = $finalResult;
             }
var_dump($tables);

once i got this into an array, i sorted it in a custom order where first the guardians with 2 kids, then with 1 kid and who has 3

ID    Guardian  kids
3     Aaron     2
6     Fred      2
1     Greg      1
5     REX       1
4     Farb      3
2     Gary      3

Now my requirement is to order this rest of the array according to its ID to descending order,

for example just like this

ID    Guardian  kids
6     Fred      2
3     Aaron     2
5     REX       1
1     Greg      1
4     Farb      3
2     Gary      3

i tried this many times but its dint work, the code i used to sort the first requirement is as follows

$order = array("2", "1", "3");

usort($tables, function ($a, $b) use ($order) {
    $pos_a = array_search($a['kids'], $order);
    $pos_b = array_search($b['kids'], $order);
    return $pos_a - $pos_b;
});

can anybody help me to fullfil my second requirement which is sort the array by ID to descending order

This is how the array looks like

array (size=3)
  0 => 
    array (size=3)
      'ID' => string '3' (length=1)
      'Guardian' => string 'Aaron' (length=5)
      'kids' => string '2' (length=1)

array (size=3)
  1 => 
    array (size=3)
      'ID' => string '6' (length=1)
      'Guardian' => string 'FRED' (length=4)
      'kids' => string '2' (length=1)

etc

P.S doing it from the table is not going to work, because im using a loop above the code which makes it impossible to do it from the SQL, can anybody tell me a way to do it from the php

Why not just put an ORDER BY on your query and have the SQL server return the data in the order you want? — GordonM
– GordonM, Commented Mar 2, 2015 at 9:16
Theres a bigger code behind this, records get added one by one using the sql, therefore the ORDER BY does not apply to it, thats why i have got it into array and sorting it — Sho Gum Lew
– Sho Gum Lew, Commented Mar 2, 2015 at 9:24

mrosiu · Accepted Answer · 2015-03-02 09:27:46Z

2

I think that it should help:

select ID,Guardian,kids
from current_state
order by case WHEN kids = 2 then 1
              WHEN kids = 1 then 2
              WHEN kids = 3 then 3
              ELSE kids END ASC
, ID desc

answered Mar 2, 2015 at 9:27

mrosiu

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Comments

merlin2011 · Accepted Answer · 2015-03-02 09:49:57Z

0

There were two primary issues.

You were using status as the first key when it should have been kids based on your description.
You need to check whether the first subtraction was zero, and if so, compare the id values.

Here is a working solution.

$order = array("2", "1", "3");

usort($tables, function ($a, $b) use ($order) {
    $pos_a = array_search($a['kids'], $order);
    $pos_b = array_search($b['kids'], $order);
    $result =  $pos_a - $pos_b;
    if ($result != 0) return $result;

    return intval($b['ID']) - intval($a['ID']);
});

var_dump($tables);

answered Mar 2, 2015 at 9:49

merlin2011

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3 Comments

merlin2011 Over a year ago

@ShoGumLew, If this does not work you'll have to edit your example, since I tested on your example. :)

Sho Gum Lew Over a year ago

no need :D this wokrs like a charm... btw can you tell me somewhere a tute or something to practice these type of sorting with "use" keyword

merlin2011 Over a year ago

@ShoGumLew, I don't know any sites that give comparator specific practice, but if you want to improve your algorithms you can look on Topcoder.

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