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up vote 1 down vote favorite

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.

share|improve this question
4  
Well, internally iteration is going to happen even if you used something like array_map() –  Michael Berkowski Dec 8 '11 at 19:08
    
Or by without iterating do you mean you just don't want a multiline foreach loop? –  Michael Berkowski Dec 8 '11 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. –  chaft Dec 8 '11 at 19:19
2  
@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 Dec 8 '11 at 19:25

3 Answers 3

up vote 4 down vote accepted

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

*/
share|improve this answer
up vote 3 down vote

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.

share|improve this answer
    
How to make it less painful with array_walk in php < 5.3? –  zerkms Dec 8 '11 at 19:10
2  
us2.php.net/array_walk check out the examples. –  Jonathan Kuhn Dec 8 '11 at 19:17
    
@Jonathan Kuhn: so you think that creating additional function less painful than to traverse it by foreach with 1 line? –  zerkms Dec 8 '11 at 20:18
    
@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). –  Dalibor Filus Dec 8 '11 at 20:22
    
@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 –  zerkms Dec 8 '11 at 20:24
up vote 0 down vote

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;   
}
share|improve this answer

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