PHP Arrays: Pop an array of single-element arrays into one array

Question

Using a proprietary framework, I am frequently finding myself in the situation where I get a resultset from the database in the following format:

array(5) {
  [0] => array(1) {
    ["id"] => int(241)
  }
  [1] => array(1) {
    ["id"] => int(2)
  }
  [2] => array(1) {
    ["id"] => int(81)
  }
  [3] => array(1) {
    ["id"] => int(560)
  }
  [4] => array(1) {
    ["id"] => int(10)
  }
}

I'd much rather have a single array of ids, such as:

array(5) {
  [0] => int(241)
  [1] => int(2)
  [2] => int(81)
  [3] => int(560)
  [4] => int(10)
}

To get there, I frequently find myself writing:

$justIds = array();
foreach( $allIds as $id ) {
  $justIds[] = $id["id"];
}

Is there a more efficient way to do this?

Are you using the good method? In most frameworks, there are methods like fetchCol() to handle the 1-dimensonal special cases... — greg0ire
– greg0ire, Commented May 31, 2010 at 16:07
It is the case that a fetchCol() style method is available, but in many cases I don't control what is actually fetching the information from the database (API calls etc). — Rob Drimmie
– Rob Drimmie, Commented May 31, 2010 at 16:37

VolkerK · Accepted Answer · 2010-05-31 16:08:03Z

9

$out = array_map('array_shift', $in);

e.g.

$in = array(
  array("id" => 241),
  array ("id" => 2),
  array ("id" => 81),
  array ("id" => 560),
  array ("id" => 10)
);
$out = array_map('array_shift', $in);
var_dump($out);

prints

array(5) {
  [0]=>
  int(241)
  [1]=>
  int(2)
  [2]=>
  int(81)
  [3]=>
  int(560)
  [4]=>
  int(10)
}

answered May 31, 2010 at 16:08

VolkerK

96.3k20 gold badges169 silver badges232 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Artefacto Over a year ago

It would probably be more efficient to use reset instead because array_shift changes the passed array. EDIT: just tested, using 'reset' gives a 6% improvement with your example on my windows debug build.

Rob Drimmie Over a year ago

What would a solution using reset look like?

VolkerK Over a year ago

Just replace array_shift by reset.

johannes · Accepted Answer · 2010-05-31 16:09:14Z

6

With PHP 5.3 you can do

$justIds = array_map(
    function($cur) {
        return $cur['id'];
    },
    $allIds
);

With PHP < 5.3 you'd have define a regular function and then pass the name as string to array_map().

answered May 31, 2010 at 16:09

johannes

16k3 gold badges47 silver badges57 bronze badges

3 Comments

johannes Over a year ago

Actually VolkerK's version with array_shift might be nicer than my custom callback

VolkerK Over a year ago

On the other hand this version works even if the input array contains arrays with more than one element regardless of the order. +1

Rob Drimmie Over a year ago

I marked VolkerK's as best answer because it addresses the specific example but there are enough times where I will need to handle multi-element sub-arrays that I will be able to add both techniques to my arsenal. Thanks to you both!

Collectives™ on Stack Overflow

PHP Arrays: Pop an array of single-element arrays into one array

2 Answers 2

3 Comments

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related