PHP - retrieve sub array value by key

Question

Given the following structure:

Array
(
    [0] => Array
        (
            [id_field] => 100
        )

    [1] => Array
        (
            [id_field] => 200
        )

    [2] => Array
        (
            [id_field] => 382
        )

    [3] => Array
        (
            [id_field] => 509
        )

    [4] => Array
        (
            [id_field] => 636
        )

    [5] => Array
        (
            [id_field] => 763
        )

    [6] => Array
        (
            [id_field] => 890
        )

    [7] => Array
        (
            [id_field] => 1017
        )

)

Is there a built in array method which can grab all id_field values?

I can loop over them for sure, but think maybe there is a built in that i cannot see in the manual that already does this?

Amal · Accepted Answer · 2014-02-18 14:37:35Z

2

If you have PHP 5.5.0+, you could use array_column():

$result = array_column($data, 'id_field');

If you're running an older PHP version, you can use the userland implentation of this function (written by the same author who wrote the original array_column() function).

However, for simple use-cases, this can be implemented as function using a simple foreach loop. This isn't guaranteed to handle all possible cases, but it should be enough for the most part.

function array_column2(array $arr, $column) {
    $result = array();
    foreach ($arr as $key => $value) {
        $result[] = $arr[$column];
    }
    return $result;
}

answered Feb 18, 2014 at 14:37

Amal

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Comments

aelgoa · Accepted Answer · 2014-02-18 14:39:43Z

0

using array filtering:

function id($var){
    return($var['id_field']);
}

print_r(array_filter($arr,"id"));

or in PHP 5.4+

print_r(array_filter($arr,  function id($var){
    return($var['id_field']);
}));

answered Feb 18, 2014 at 14:39

aelgoa

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ilhnctn · Accepted Answer · 2014-02-18 14:39:59Z

0

array_keys() is what you are looking for.

sample from docs:

<?php
$array = array(0 => 100, "color" => "red");
print_r(array_keys($array));

$array = array("blue", "red", "green", "blue", "blue");
print_r(array_keys($array, "blue"));

$array = array("color" => array("blue", "red", "green"),
               "size"  => array("small", "medium", "large"));
print_r(array_keys($array));
?>

and it's output:

Array
(
    [0] => 0
    [1] => color
)
Array
(
    [0] => 0
    [1] => 3
    [2] => 4
)
Array
(
    [0] => color
    [1] => size
)

answered Feb 18, 2014 at 14:39

ilhnctn

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