Please, don't invent your own implementation of array_column(). The author of this function already provides a version written in plain PHP:
https://github.com/ramsey/array_column
See also:
http://benramsey.com/blog/2013/07/the-array-column-php-userland-library/
array_column
(PHP 5 >= 5.5.0)
array_column — Return the values from a single column in the input array
Description
array_column() returns the values from a single column of
the array, identified by the
column_key. Optionally, you may provide an
index_key to index the values in the returned array by
the values from the index_key column in the input
array.
Parameters
-
array -
A multi-dimensional array (record set) from which to pull a column of values.
-
column_key -
The column of values to return. This value may be the integer key of the column you wish to retrieve, or it may be the string key name for an associative array. It may also be
NULLto return complete arrays (useful together withindex_keyto reindex the array). -
index_key -
The column to use as the index/keys for the returned array. This value may be the integer key of the column, or it may be the string key name.
Return Values
Returns an array of values representing a single column from the input array.
Examples
Example #1 Get column of first names from recordset
<?php
// Array representing a possible record set returned from a database
$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',
)
);
$first_names = array_column($records, 'first_name');
print_r($first_names);
?>
The above example will output:
Array
(
[0] => John
[1] => Sally
[2] => Jane
[3] => Peter
)
Example #2 Get column of last names from recordset, indexed by the "id" column
<?php
// Using the $records array from Example #1
$last_names = array_column($records, 'last_name', 'id');
print_r($last_names);
?>
The above example will output:
Array
(
[2135] => Doe
[3245] => Smith
[5342] => Jones
[5623] => Doe
)
add a note
User Contributed Notes 5 notes
fireweasel@wirefeasel ¶
8 months ago
vovan-ve at yandex dot ru ¶
9 months ago
>>> for < PHP5.5 , following function can be used :
NEVER edit items of array argument by reference! It WILL damage items of original array, which are referenced outside with another variables like this:
$foo = array(10, 20, 30);
$bar = &$foo[1];
You should just to collect a new array instead of changing array by reference.
So, userland implementation can be such a following:
# PHP < 5.5
function array_column(array $input, $columnKey, $indexKey = null) {
$result = array();
if (null === $indexKey) {
if (null === $columnKey) {
// trigger_error('What are you doing? Use array_values() instead!', E_USER_NOTICE);
$result = array_values($input);
}
else {
foreach ($input as $row) {
$result[] = $row[$columnKey];
}
}
}
else {
if (null === $columnKey) {
foreach ($input as $row) {
$result[$row[$indexKey]] = $row;
}
}
else {
foreach ($input as $row) {
$result[$row[$indexKey]] = $row[$columnKey];
}
}
}
return $result;
}
ohcc at 163 dot com ¶
2 months ago
This function will fail when you try to fetch columns from an indexed array.
<?php
$a =array(
array(1,2,3),
array(4,5,6),
array(7,8,9)
);
print_r(array_column($a,'0'));
?>
Expected results should be :
Array
(
[0] => 1
[1] => 4
[2] => 7
)
But we get :
Array (
)
Instead I have create another function.
<?php
function my_array_column($array,$colName){
$results=array();
if(!is_array($array)) return $results;
foreach($array as $child){
if(!is_array($child)) continue;
if(array_key_exists($colName,$child)){
$results[] = $child[$colName];
}
}
return $results;
}
$a =array(
array(1,2,3),
array(4,5,6),
array(7,8,9)
);
print_r(my_array_column($a,'0'));
?>
Now we get the right results:
Array
(
[0] => 1
[1] => 4
[2] => 7
)
WARrior ¶
5 months ago
You can also use array_map fucntion if you haven't array_column().
example:
$a = array(
array(
'id' => 2135,
'first_name' => 'John',
'last_name' => 'Doe',
),
array(
'id' => 3245,
'first_name' => 'Sally',
'last_name' => 'Smith',
)
);
array_column($a, 'last_name');
becomes
array_map(function($element){return $element['last_name']}, $a)
jan venekamp ¶
8 months ago
Implementation for PHP < 5.5.0
Following: https://wiki.php.net/rfc/array_column
<?php
// PHP < 5.5.0
if (!function_exists('array_column')) {
function array_column($input, $column_key, $index_key = null)
{
if ($index_key !== null) {
// Collect the keys
$keys = array();
$i = 0; // Counter for numerical keys when key does not exist
foreach ($input as $row) {
if (array_key_exists($index_key, $row)) {
// Update counter for numerical keys
if (is_numeric($row[$index_key]) || is_bool($row[$index_key])) {
$i = max($i, (int) $row[$index_key] + 1);
}
// Get the key from a single column of the array
$keys[] = $row[$index_key];
} else {
// The key does not exist, use numerical indexing
$keys[] = $i++;
}
}
}
if ($column_key !== null) {
// Collect the values
$values = array();
$i = 0; // Counter for removing keys
foreach ($input as $row) {
if (array_key_exists($column_key, $row)) {
// Get the values from a single column of the input array
$values[] = $row[$column_key];
$i++;
} elseif (isset($keys)) {
// Values does not exist, also drop the key for it
array_splice($keys, $i, 1);
}
}
} else {
// Get the full arrays
$values = array_values($input);
}
if ($index_key !== null) {
return array_combine($keys, $values);
}
return $values;
}
}
?>
