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Request for Comments: array_column

Version: 1.0
Date: 2012-06-21
Author: Ben Ramsey ramsey@php.net
Status: Under Discussion
First Published at: http://wiki.php.net/rfc/array_column

Introduction

This RFC proposes a new array function that returns the values of the specified column from a multi-dimensional array. Inspired by database methods like PDOStatement::fetchColumn(), array_column() moves useful functionality into the core that once had to be implemented in userland code with sometimes complex loops.

This has been submitted as a pull request on GitHub, where there has already been a significant amount of discussion.

Specification

Description

array array_column(array $input, mixed $key)

array_column() returns the values from a single column of the input array, identified by the key.

Parameters

input

A multi-dimensional array (record set) from which to pull a column of values.

key

The column of values to return. This value may be the 0-indexed number of the column you wish to retrieve, or it may be the string key name for an associative array.

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' => 1,
        'first_name' => 'John',
        'last_name' => 'Doe'
    ),
    array(
        'id' => 2,
        'first_name' => 'Sally',
        'last_name' => 'Smith'
    ),
    array(
        'id' => 3,
        'first_name' => 'Jane',
        'last_name' => 'Jones'
    )
);
 
$firstNames = array_column($records, 'first_name');
print_r($firstNames);

The above example will output:

Array
(
    [0] => John
    [1] => Sally
    [2] => Jane
)

Example #2: Retrieve a column of values from a numerically-indexed array

<?php
$records = array(
    array(1, 'John', 'Doe'),
    array(2, 'Sally', 'Smith'),
    array(3, 'Jane', 'Jones')
);
 
$firstNames = array_column($records, 2);
print_r($firstNames);