Extract line or column from PHP array

Question

I have a bidimensional PHP array (matrix).

Is there anyway to extract (echo or save into another variable) a line or a column from this matrix without iterating through the elements?

Suppose we have this matrix:

A A A B
A A A C
A B C D

I want to do something like:

display_and_cut_first_line()

//Matrix after this step:    
A A A C
A B C D

display_and_cut_last_column()
//Matrix after this step:
A A A
A B C

It only has to work for marginal elements (first/last line, first/last column). I was thinking of somehow using slice, but didn't manage to do it.

Upgrade to PHP5.5 as soon as it's available, and get access to the array_column() function - benramsey.com/blog/2013/03/… — Mark Baker
– Mark Baker, Commented Jun 7, 2013 at 8:39

Jon · Accepted Answer · 2015-02-23 10:23:39Z

6

Extracting lines is easy: array_pop (last line) and array_shift (first line) do this for you.

Extracting columns is very easy on PHP 5.5 with array_column. For earlier versions it would have to be done manually with array_map or array_walk and the pop/shift functions, operating on each line in turn:

function extract_last_column(&$array) {
    $column = array();
    array_walk($array, function(&$row) use(&$column) {
        $column[] = array_pop($row);
    });
    return $column;
}

See it in action.

If desired you can generalize this by using array_slice instead of array_pop and array_shift -- but for these particular operations it will be slower.

edited Feb 23, 2015 at 10:23

answered Jun 7, 2013 at 8:27

Jon

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6 Comments

Benubird Over a year ago

Think you might mean echo array_pop($a); as OP wants to echo the values cut.

IMSoP Over a year ago

If you can get it to return the removed section, like array_pop et al would, that would be even better, I would have thought.

Jon Over a year ago

@IMSoP: Finished and added a live example. Works like you describe.

Jon Over a year ago

@IMSoP: Thank you. I think I produced something neater yesterday, you might find it amusing.

XCS Over a year ago

Great, but here comes a problem: I do this until the matrix is empty. The problem is that this will not work if the array is uni-dimensional (array_walk will iterate through integer values and try to use array_pop on those, resulting in an error). How can I check if an array is uni-dimensional? (is one line or one column only)

|

Benubird · Accepted Answer · 2013-06-07 08:28:24Z

0

Yes. To get the first row:

$arr[0];

To get the last column:

$keys = array_keys($arr);
array_column($arr, end($keys));

answered Jun 7, 2013 at 8:28

Benubird

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1 Comment

IMSoP Over a year ago

I'd never heard of array_column(), which isn't surprising, as it's only introduced in PHP 5.5, which (still!) isn't officially a stable release yet. Interesting to know for future reference though...

Josua M C · Accepted Answer · 2013-06-07 08:49:06Z

<?php 
$example = array();
$example[0][0] = 'A';$example[0][1] = 'A';$example[0][2] = 'A';$example[0][3] = 'B';
$example[1][0] = 'A';$example[1][1] = 'A';$example[1][2] = 'A';$example[1][3] = 'C';
$example[2][0] = 'A';$example[2][1] = 'B';$example[2][2] = 'C';$example[2][3] = 'D';

$example = display_and_cut_first_line($example);
print_r($example);
/* Array
(
    [0] => Array
        (
            [0] => A
            [1] => A
            [2] => A
            [3] => C
        )

    [1] => Array
        (
            [0] => A
            [1] => B
            [2] => C
            [3] => D
        )

)
 */
$example = display_and_cut_last_column($example);
print_r($example);
/* Array
(
    [0] => Array
        (
            [0] => A
            [1] => A
            [2] => A
        )

    [1] => Array
        (
            [0] => A
            [1] => B
            [2] => C
        )

)
 */
function display_and_cut_first_line($array){
    array_shift($array);
    return ($array);
}

function display_and_cut_last_column($array){
    $result = array();
    foreach($array as $data):
        array_pop($data);
        $result[] = $data;
    endforeach;

    return $result;
}

?>

Bas Cost Budde · Accepted Answer · 2013-06-07 08:30:33Z

-2

Partly.

Cutting out a line can be done, using array_splice().

A "column" is not a recognisable entry in the array implementation, so you have to at least iterate the rows, possibly using array_map().

answered Jun 7, 2013 at 8:30

Bas Cost Budde

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