Is there a function to extract a 'column' from an array in PHP?

Question

I have an array of arrays, with the following structure :

array(array(\'page\' => \'page1\', \'name\' => \'pagename1\')
      array(\'page\' => \'pa         


        

Answer 1

if (!function_exists('array_column')) {
    function array_column($array,$column) {
    $col = array();
    foreach ($array as $k => $v) {
        $col[]=$v[$column];
    }
    return $col;
    }
}

This should work for php versions < 5.5 and degrade in case the function exist

Answer 2

Well there is. At least for PHP > 5.5.0 and it is called array_column

The PHP function takes an optional $index_keyparameter that - as per the PHP website - states:

$index_key

The column to use as the index/keys for the returned array. This value may be the integer key of the column, or it may be the string key name

In the answers here, i see a stripped version without the optional parameter. I needed it, so, here is the complete function:

if (!function_exists('array_column')) {
    function array_column($array, $column, $index_key = null) {
        $toret = array();
        foreach ($array as $key => $value) {
            if ($index_key === null){
                $toret[] = $value[$column];
            }else{
                $toret[$value[$index_key]] = $value[$column];
            }
        }
        return $toret;
    }
}

Answer 3

There is a built-in function actually, it's called array_column(...).

Here is all you need to know about it : https://www.php.net/manual/fr/function.array-column.php

Answer 4

You can extend the ArrayIterator class and override the method mixed current(void).

class Foo extends ArrayIterator {
  protected $index;
  public function __construct($array, $index) {
    parent::__construct($array);
    $this->index = $index;
  }

  public function current() {
    $c = parent::current();
    return isset($c[$this->index]) ? $c[$this->index] : null;
  }
}

$a = array(
  array('page' => 'page1', 'name' => 'pagename1'),
  array('name' => '---'),
  array('page' => 'page2', 'name' => 'pagename2'),
  array('page' => 'page3', 'name' => 'pagename3')
);

$f = new Foo($a, 'page');
foreach($f as $e) {
  echo $e, "\n";
}

prints

page1

page2
page3

Answer 5

As of PHP 5.5 you can use array_column():

<?php
$samples=array(
            array('page' => 'page1', 'name' => 'pagename1'),
            array('page' => 'page2', 'name' => 'pagename2'),
            array('page' => 'page3', 'name' => 'pagename3')
            );
$names = array_column($samples, 'name');
print_r($names);

See it in action

Answer 6

I wanted to post here, even if this is an old question, because it is still very relevant and many developers do not use PHP >= 5.5

Let's say you have an array like this:

Array
(
    [files] => Array
        (
            [name] => Array
                (
                    [0] => file 1
                    [1] => file 2
                    [2] => file 3
                )

            [size] => Array
                (
                    [0] => 1
                    [1] => 2
                    [2] => 3
                )

            [error] => Array
                (
                    [0] => abc
                    [1] => def
                    [2] => ghi
                )

        )

)

and the output you want is something like this:

Array
(
    [0] => Array
        (
            [0] => file 1
            [1] => 1
            [2] => abc
        )

    [1] => Array
        (
            [0] => file 2
            [1] => 2
            [2] => def
        )

    [2] => Array
        (
            [0] => file 3
            [1] => 3
            [2] => ghi
        )

)

You can simply use the array_map() method without a function name passed as the first parameter, like so:

array_map(null, $a['files']['name'], $a['files']['size'], $a['files']['error']);

Unfortunately you cannot map the keys if passing more than one array.