Isolate a single column in a multi-dimensional array - php

Question

Say for example you just queried a database and you recieved this 2D array.
$results = array(
array('id' => 1, 'name' => 'red' , 'spin' => 1),
array('id' => 2, 'name' => 'green', 'spin' => -1),
array('id' => 3, 'name' => 'blue' , 'spin' => .5)
);
I often find myself writing loops like this.
foreach($results as $result)
$names[] = $result['name'];
My questions is does there exist a way to get this array $names without using a loop? Using callback functions count as using a loop.
Here is a more generic example of getting every field.
foreach($results as $result)
foreach($result as $key => $value)
$fields[$key][] = $value;

Answer 1

As of June 20th in PHP-5.5 there is a new function array_column
For example:
$records = array(
array(
'id' => 2135,
'first_name' => 'John',
'last_name' => 'Doe'
),
array(
'id' => 3245,
'first_name' => 'Sally',
'last_name' => 'Smith'
),
array(
'id' => 5342,
'first_name' => 'Jane',
'last_name' => 'Jones'
),
array(
'id' => 5623,
'first_name' => 'Peter',
'last_name' => 'Doe'
)
);
$firstNames = array_column($records, 'first_name');
print_r($firstNames);
Will return
Array
(
[0] => John
[1] => Sally
[2] => Jane
[3] => Peter
)
There are even more examples in the above mentioned link.

Answer 2

I voted #Devon's response up because there really isn't a way to do what you're asking with a built-in function. The best you can do is write your own:
function array_column($array, $column)
{
$ret = array();
foreach ($array as $row) $ret[] = $row[$column];
return $ret;
}

Answer 3

Starting PHP 5.3, you can use this pretty call with lambda function:
$names = array_map(function ($v){ return $v['name']; }, $results);
This will return array sliced by 'name' dimension.

Answer 4

Simply put, no.
You will need to use a loop or a callback function like array_walk.

Answer 5

I did more research on this and found that ruby and prototype both have a function that does this called array_pluck,2. It's interesting that array_map has a second use that allows you to do the inverse of what i want to do here. I also found a PHP class someone is writing to emulate prototypes manipulation of arrays.
I'm going to do some more digging around and if I don't find anything else I'll work on a patch to submit to the internals#lists.php.net mailing list and see if they will add array_pluck.

Answer 6

For those of you that cannot upgrade to PHP5.5 right now and need this function, here is an implementation of array_column.
function array_column($array, $column){
$a2 = array();
array_map(function ($a1) use ($column, &$a2){
array_push($a2, $a1[$column]);
}, $array);
return $a2;
}

Answer 7

If you are running a version of PHP before 5.5 and array_column(), you can use the official replacement in plain PHP:
https://github.com/ramsey/array_column

Answer 8

I think this will do what you want
array_uintersect_uassoc
You would have to do something like this
$results = array(
array('id' => 1, 'name' => 'red' , 'spin' => 1),
array('id' => 2, 'name' => 'green', 'spin' => -1),
array('id' => 3, 'name' => 'blue' , 'spin' => .5)
);
$name = array_uintersect_uassoc( $results, array('name' => 'value') , 0, "cmpKey");
print_r($name);
//////////////////////////////////////////////////
// FUNCTIONS
//////////////////////////////////////////////////
function cmpKey($key1, $key2) {
if ($key1 == $key2) {
return 0;
} else {
return -1;
}
}
However, I don't have access to PHP5 so I haven't tested this.

Answer 9

You could do:
$tmp = array_flip($names);
$names = array_keys($tmp);

Answer 10

This is fast function alternative of array_column()
if(!function_exists('array_column')) {
function array_column($element_name) {
$ele = array_map(function($element) {
return $element[$element_name];
}, $a);
return $ele;
}
}

Answer 11

other alternative
function transpose(array $array): array
{
$out = array();
foreach ($array as $rowkey => $row) {
foreach ($row as $colkey => $col) {
$out[$colkey][$rowkey] = $col;
}
}
return $out;
}
function filter_columns(array $arr, string ...$columns): array
{
return array_intersect_key($arr, array_flip($columns));
}
test
$results = array(
array('id' => 1, 'name' => 'red' , 'spin' => 1),
array('id' => 2, 'name' => 'green', 'spin' => -1),
array('id' => 3, 'name' => 'blue' , 'spin' => .5)
);
var_dump(filter_columns(transpose($results),'name'));
var_dump(filter_columns(transpose($results),'id','name'));
var_dump(filter_columns(transpose($results),'id','spin'));