restructure a multidimentional array in php based on its values

Question

I have a multi dimentional php array like this :

where the column "b" has 2 possible values ( x, y) and column "v" has 2 possible values ( t,f )

Array
(
[0] => Array
    (
        [a] => 6
        [b] => x
        [c] => t
    )

[1] => Array
    (
        [a] => 4
        [b] => x
        [c] => t
    )
[2] => Array
    (
        [a] => 6
        [b] => y
        [c] => f
    )

I want to rearrange the columns so that they are structured by values , in the following way.

My Question is, is there a smart way to do this using some native php functions , without looping through everything

Array(
    [value of b=x] => Array(
        [value of c=t] => Array( all ids in the array)
        [value of c=f] => Array( all ids in the array)
     )
    [value of b=y] => Array(
        [value of c=t] => Array( all ids in the array)
        [value of c=f] => Array( all ids in the array)
     )

  )

Even if there was a native function that did exactly that, what's wrong with looping? The native function would have to loop as well behind the scenes. — deceze
– deceze ♦, Commented Apr 27, 2012 at 10:24

DaveRandom · Accepted Answer · 2012-04-27 10:10:25Z

2

I assume that by all ids in the array you mean "all the a column values in the array". In which case, this is what you want:

$result = array();

array_walk($array, function($val, $key) use (&$result) {
  $result[$val['b']][$val['c']][] = $val['a'];
});

print_r($result);

If by ids you mean the outer array indices, simply change $val['a'] to $key in the above code.

answered Apr 27, 2012 at 10:10

DaveRandom

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4 Comments

deceze Over a year ago

I'd just go with a foreach instead of array_walk, it's really the same thing in different disguise.

DaveRandom Over a year ago

@deceze I know and I agree 100%, especially since a lot of the world still runs on <5.3 (no closures) and it makes scoping much easier to cope with, but he asked for a native function implementation, so a native function implementation he shall have. One point about that which someone made to me recently though is that (if you're of a micro-optimisation disposition) a C++ loop is more efficient than a PHP loop.

deceze Over a year ago

I'd agree that the C++ loop is faster, but wonder if that isn't negated by the function call overhead...

Nauman Bashir Over a year ago

thanks Dave, actually i did something like that, but was looking if there was any other way..

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