PHP multidimensional array conversion using array_map/array_walk functions

Question

I have the following multidimensional array:

$userList = array(
    0 => array('id' => 1000, 'first_name' => 'John', 'last_name' => 'Smith'),
    1 => array('id' => 1001, 'first_name' => 'Sam', 'last_name' => 'Johnson'),
);

I want to convert it to the array like:

$userData = array(
    1000 => 'John Smith',
    1001 => 'Sam Johnson',
);

It's quite obvious for me how to implement this using foreach loop, but I wonder if it's possible to do this with PHP array functions like array_map or array_walk. Please use PHP 5.3 for the callback function. Thank you!

Answer 1

Since those functions only work on the array values, getting them to set the key in the new array is somewhat awkward. One way to do it is:

$arr = array_combine(
    array_map(function ($i) { return $i['id']; }, $arr),
    array_map(function ($i) { return "$i[first_name] $i[last_name]"; }, $arr)
);

This is a case where a foreach is much more appropriate.

Answer 2

A minor trick from the functional programming.

$arr = array_reduce(
  $arr,
  function ($result, $item) {
    $result[$item['id']] = $item['first_name'] . ' ' . $item['last_name'];
    return $result;
  },
  array()
);

See array_reduce().

Answer 3

Code:

<?php

function convertArray ( $array ) {

    $newUserList = array();
    foreach ( $array as $value ) {
        $newUserList[ $value[ 'id' ] ] = $value[ 'first_name' ] . ' ' . $value[ 'last_name' ];
    }

    return $newUserList;

}   

$userList = array(
    0 => array( 'id' => 1000, 'first_name' => 'John', 'last_name' => 'Smith' ),
    1 => array( 'id' => 1001, 'first_name' => 'Sam', 'last_name' => 'Johnson' )
);

$newUserList = convertArray( $userList );

?>

Output:

Array
(
    [1000] => John Smith
    [1001] => Sam Johnson
)