PHP - unset in a multidimensional array

Question

I have this array $output which looks like this:

Array(
    [0] => Array(
        [0] => 1a
        [1] => 1b
        [2] => 1c
    )
    [1] => Array(
        [0] => 2a
        [1] => 2b
        [2] => 2c
    )
    [2] => Array(
        [0] => 3a
        [1] => 3b
        [2] => 3c
    )
    [3] => Array(
        [0] => 4a
        [1] => 4b
        [2] => 4c
    )
)

and so on...

When I want to remove the second element I just use

$output = unset($output[1]);

to get the following:

Array(
    [0] => Array(
        [0] => 1a
        [1] => 1b
        [2] => 1c
    )
    [1] => Array(
        [0] => 3a
        [1] => 3b
        [2] => 3c
    )
    [2] => Array(
        [0] => 4a
        [1] => 4b
        [2] => 4c
    )
)

My question is how to remove every second element of every element in the array ([0][1], [1][1], [2][1], [3][1] ,...) to get the following:

Array(
    [0] => Array(
        [0] => 1a
        [1] => 1c
    )
    [1] => Array(
        [0] => 2a
        [1] => 2c
    )
    [2] => Array(
        [0] => 3a
        [1] => 3c
    )
    [3] => Array(
        [0] => 4a
        [1] => 4c
    )
)

Answer 1

Can't be done with a simple command, but you can use a loop:

foreach(array_keys($output) as $key) {
   unset($output[$key][1]);
}

Answer 2

Clean and neat:

$f=function(&$a,$k) { unset $a[1]; };
array_walk($arr,$f);

Answer 3

You can iterate over the array, and unset() what you want in each sub-array:

foreach($output as &$item) {
    unset($item[2]);
}
unset($item); // unset reference

Answer 4

foreach($array as $key=>$val){ unset($val[1]); }

Answer 5

You'd use a combination of array_map and array_splice:

function removeSecond( array &$arr )
{
    array_splice( $arr, 1, 1 );
}
$out = array_map( 'removeSecond', $input );

The problem with unset is that it will leave the indexes as they were:

$ php -r '$arr = array(array(0,1,2)); unset($arr[0][1]); var_dump($arr);'
array(1) {
  [0]=>
  array(2) {
    [0]=>
    int(0)
    [2]=>
    int(2)
  }
}

While splice will update the indexes:

$ php -r '$arr = array(array(0,1,2)); array_splice($arr[0], 1, 1); var_dump($arr);'
array(1) {
  [0]=>
  array(2) {
    [0]=>
    int(0)
    [1]=>
    int(2)
  }
}