PHP Add element to every sub array of multi dimension array

Question

I have an array that looks something like that

array(
     [0] => array(
               'id' => 1,
               'title' => 'title 1',
     ),
     [1] => array(
               'id' => 10,
               'title' => 'title 10',
     ),
     [2] => array(
               'id' => 11,
               'title' => 'title 11',
     ),
     [...]
);

I want to add an element to all the sub array. It's the same element i'm adding. so the new array will look like :

array(
     [0] => array(
               'id' => 1,
               'title' => 'title 1',
               'type'  => 'bag',
     ),
     [1] => array(
               'id' => 10,
               'title' => 'title 10',
               'type'  => 'bag',
     ),
     [2] => array(
               'id' => 11,
               'title' => 'title 11',
               'type'  => 'bag',
     ),
     [...]
);

~~Is there a way to do it without iterating on the the first array?~~ It's gonna be a big array. I'm looking for the fastest way to do it.

Well, internally iteration is going to happen even if you used something like array_map() — Michael Berkowski
– Michael Berkowski, Commented Dec 8, 2011 at 19:08
Or by without iterating do you mean you just don't want a multiline foreach loop? — Michael Berkowski
– Michael Berkowski, Commented Dec 8, 2011 at 19:09
It's an array from with results from a db (up to a few hundreds). I assume a foreach loop will be slow. hence without iterating. I meant a fast way. — applechief
– applechief, Commented Dec 8, 2011 at 19:19
@chaft: You assume. Have you tested it? An array with a few hundred (or thousand, for that matter) elements in it will be iterated in a few milliseconds. And even array_walk() iterates the array internally, there is no magic involved. ;) — Tomalak
– Tomalak, Commented Dec 8, 2011 at 19:25

webbiedave · Accepted Answer · 2011-12-08 19:44:59Z

Whatever speed one might hope to gain by using array_walk, is lost with function overhead. Since you stated in your comments that the array is a result of a db query, you can simply include the bag value in your result set by adding SELECT 'bag' AS 'type' to your SQL statement.

$start = 0; $end = 0;

$orig = array(
    array('id' => 1,  'title' => 'title 1'),
    array('id' => 10, 'title' => 'title 10'),
    array('id' => 11, 'title' => 'title 11')
);

// A
$start = microtime(true);
for ($a=0; $a<1000; $a++) {
    $els1 = $orig;
    array_walk($els1, function(&$val, $key){$val['type'] = 'bag';});
}
$end = microtime(true);
echo 'A: ', $end - $start,  "<br />\n";

// B
$start = microtime(true);
for ($b=0; $b<1000; $b++) {
    $els2 = $orig;
    foreach ($els2 as &$el) {
        $el['type'] = 'bag';
    }
    unset($el);
}
$end = microtime(true);
echo 'B: ', $end - $start,  "<br />\n";

/* output:

A: 0.0076138973236084
B: 0.0047528743743896

A: 0.0075309276580811
B: 0.0045361518859863

A: 0.0075531005859375
B: 0.062379837036133

A: 0.0075340270996094
B: 0.0044951438903809

A: 0.0074868202209473
B: 0.0044751167297363

A: 0.0076088905334473
B: 0.0048189163208008

*/

Dalibor Filus · Accepted Answer · 2011-12-08 20:45:22Z

3

Logically, no, there isn't any way to do it without iterating the parent array. ~~But you can make it less painful by using array_walk().~~ EDIT: benchmark shows array_walk (or array-_map) is slower by a third, so I take this back.

edited Dec 8, 2011 at 20:45

answered Dec 8, 2011 at 19:09

Dalibor Filus

1,31614 silver badges21 bronze badges

6 Comments

zerkms Over a year ago

How to make it less painful with array_walk in php < 5.3?

zerkms Over a year ago

@Jonathan Kuhn: so you think that creating additional function less painful than to traverse it by foreach with 1 line?

Dalibor Filus Over a year ago

@zerkms yes. array_walk iterates internally, without opcode processing overhead. Try this and see how long it runs: foreach(range(1,1000000) as $i) {}; (yes, empty loop taking XX seconds. Rewrite that to for($i = 0; $i < 1000000; $i++) {} and it will take even more).

zerkms Over a year ago

@NoICE: dude, you told about array_walk() as less painful solution. So I asked you how in php < 5.3 it can be less painful. Where for vs foreach came from?! Have you seen the answer above yours: stackoverflow.com/a/8436642/251311 ??? iterates internally -- yes, it does iterate internally, BUT it calls a function. Function call is much more expensive than just assignment

Dalibor Filus Over a year ago

@zerkms less painful [than iterating it manually -> and what keywords we use for iterating? for and foreach.]. Also, by "less painful" I ment "less painful for the server, for performance hit". Function call in php is fast and in this case it is done internally, too (though I don't have that confirmed, maybe foreach with reference assignment is faster for this purpose. As I think about it it should. Wait a minute, I will benchmark it. ... Oh I've just noticed that someone already did that, so you are right, foreach is faster for this purpose.. even if it is just by 3 miliseconds :D ).

|

Westy · Accepted Answer · 2014-08-15 10:07:43Z

3

From a simple/clean code point of view this solution suits:

$orig = array(
array('id' => 1,  'title' => 'title 1'),
array('id' => 10, 'title' => 'title 10'),
array('id' => 11, 'title' => 'title 11'));

foreach($orig as $key => $value)
{
    $value['type'] = 'bag';
    $orig[$key] = $value;   
}

answered Aug 15, 2014 at 10:07

Westy

937 bronze badges

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