PHP: merge unknown number of arrays

Question

I have one big array structured like this

$array = array(

   [0] => array(
      'labels' => array('a', 'b', 'c', [...]),
      'values' => array('val A', 'val B', 'val C', [...])
   ),

   [1] => array(
      'labels' => array('d', 'e', 'f', [...]),
      'values' => array('val D', 'val E', 'val F', [...])
   ),

   [2] => array(
      'labels' => array([...]),
      'values' => array([...])
   ),

   [...],

   [n]

)

I want to create a new array for every key, like so:

$labels = array('a', 'b', 'c', 'd', 'e', 'f', [...])
$values = array('val A', 'val B', 'val C', 'val D', 'val E', 'val F', [...])

I would normally use array_merge, but I don't know how many arrays I will have.

Is there any way of doing it without looping multiple times ?

Thank you

Using individual variables seems like a missed opportunity to sensibly use arrays. There is no downside to populating an array of rows where you can quickly access data by associative key. — mickmackusa, Oct 10 '22 at 22:57

score 2 · Answer 1 · answered Jan 25 '16 at 12:53

2

Something like:

$labels = call_user_func_array('array_merge', array_column($array, 'labels'));
$values = call_user_func_array('array_merge', array_column($array, 'values'));

perhaps?

answered Jan 25 '16 at 12:53

Mark Baker

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If you use PHP5.6, you can reduce this code to : `array_merge(...array_column($array, 'labels'))` More elegant imho ;) – JesusTheHun Jan 25 '16 at 13:07
Unfortunately I have 5.3 on the client's hosting, so I cannot use your method. It's a shame because I like one liners. – C. Ovidiu Jan 25 '16 at 13:16

score 1 · Accepted Answer · answered Jan 25 '16 at 13:00

1

If you want to do some manipulations before building the final array, consider something like this :

$labels = array();
$values = array();

$r = array_map(function($subArray) use(&$labels, &$values) {

    // do some stuff here, maybe

    $labels = array_merge($labels, $subArray['labels']);
    $values = array_merge($values, $subArray['values']);

}, $array);

answered Jan 25 '16 at 13:00

JesusTheHun

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With some tweaks this also works, but I will use Mark's answer. Thank you – C. Ovidiu Jan 25 '16 at 13:02
Yep, ok. Beware you need PHP 5.5+ to use Mark's answer. – JesusTheHun Jan 25 '16 at 13:04
Didn't check the version requirement, so your method is the correct one in my case. Thank you again – C. Ovidiu Jan 25 '16 at 13:17

PHP: merge unknown number of arrays

2 Answers2