Get all values of a specific column in a multidimensional array [duplicate]

Question

I have a multidimensional array, that has say, x number of columns and y number of rows.

I want specifically all the values in the 3rd column.

The obvious way to go about doing this is to put this in a for loop like this

for(i=0;i<y-1;i++)
{
   $ThirdColumn[] = $array[$i][3];
}

but there is an obvious time complexity of O(n) involved here. Is there a built in way for me to simply extract each of these rows from the array without having to loop in.

For example (this does not work offcourse)

$ThirdColumn  = $array[][3]

Answer 1

Given a bidimensional array $channels:

$channels = array(
    array(
        'id' => 100,
        'name' => 'Direct'
    ),
    array(
        'id' => 200,
        'name' => 'Dynamic'
    )
);

A nice way is using array_map:

$_currentChannels = array_map(function ($value) {
    return  $value['name'];
}, $channels);

and if you are a potentate (php 5.5+) through array_column:

$_currentChannels = array_column($channels, 'name');

Both results in:

Array
(
    [0] => Direct
    [1] => Dynamic
)

---

Star guests: array_map (php4+) and array_column (php5.5+)

// array array_map ( callable $callback , array $array1 [, array $... ] )
// array array_column ( array $array , mixed $column_key [, mixed $index_key = null ] )

Answer 2

Is there a built in way for me to simply extract each of these rows from the array without having to loop in.

Not yet. There will be a function soon named array_column(). However the complexity will be the same, it's just a bit more optimized because it's implemented in C and inside the PHP engine.