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I have a list of arrays (or objects, they are coming from a database via the PDO fetchAll() function, so both options are OK for me). I wish to convert the list of arrays to an associative array of arrays with the key of each array being one of its columns.

I can obviously do a loop, but I am wondering whether there is some PHP function which already does this, maybe in a more efficient way.

So to illustrate it, lets say I have an array (non-associative) with arrays inside: 

[0] => {'name' : 'Joe', 'surname' : 'Bloggs', 'id' : '12345'}
[1] => {'name' : 'Sandy', 'surname' : 'Smith', 'id' : '54321'}

I wish to convert it to:

['12345'] => {'name' : 'Joe', 'surname' : 'Bloggs', 'id' : '12345'}
['54321'] => {'name' : 'Sandy', 'surname' : 'Smith', 'id' : '54321'}
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  • Do you have objects or arrays ? Commented Apr 17, 2013 at 23:00
  • @adeneo I have associative arrays (internally) at the moment, but I can change them easily to objects if needed. Just a question of changing to PDO::FETCH_OBJ. So both options OK for me if an elegant technique exists (which does not involve looping). Commented Apr 17, 2013 at 23:06

2 Answers 2

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A simple loop would do, but that's too boring to post an answer for, so here you go:

$array = array_combine(array_map(function (array $row) { return $row['id']; }, $array),
                       $array);

If you're partial to functional PHP:

$array = array_combine(F\pluck($array, 'id'), $array);
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9 Comments

LOL :), well yeah not looking for a simple loop which I can easily do. Do you think this is more efficient?
No, since it 1) loops over the array twice and 2) stores a separate array of ids in memory. You could optimize that with a loop. Probably doesn't make a lot of difference for average array sizes though.
As far as I know the array_map function needs a "callable" as first param, and an array is not..
@arraintxo Dayum, right. The argument order keeps tripping me up. :)
@deceze Functional PHP? Thats not standard PHP right? Interesting though!
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$rows = $stmt->fetch(PDO::FETCH_ASSOC);

or

$rows = $stmt->fetchall(PDO::FETCH_ASSOC);

Let's read what HashPHP said:

Note the use of PDO::FETCH_ASSOC in the fetch() and fetchAll() code above. This tells PDO to return the rows as an associative array with the field names as keys. Other fetch modes like PDO::FETCH_NUM returns the row as a numerical array. The default is to fetch with PDO::FETCH_BOTH which duplicates the data with both a numerical and associative keys. It's recommended you specify one or the other so you don't have arrays that are double the size! PDO can also fetch objects with PDO::FETCH_OBJ, and can take existing classes with PDO::FETCH_CLASS. It can also bind into specific variables with PDO::FETCH_BOUND and using bindColumn method.

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3 Comments

How will it know which column I want to be the key in the associative array? I think that works on the internal individual arrays (which I am already doing) I am looking at the outer array.
this will produce his 1st array, not the one he wants!
As @michi says that would not return the array he wants, just the one he allready has.

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