PHP: Array support class and functions

Arr.php

<?php
/**
 * Support class for working with arrays.
 */
class Arr
{

  /**
   * Extend an associative array.
   *
   * Values in $option array overwrite those in $default, but only for keys
   * which are present in $default. All other keys are discarded.
   *
   * @access public
   *
   * @param  array  $default
   * @param  array  $options
   * @return array
   */
  public static function extend( array $default, array $options ) : array
  {
    return array_intersect_key( array_merge( $default, $options ), $default );
  }

  /**
   * Pluck values from a collection of arrays or objects.
   *
   * @access public
   *
   * @param  array   $array
   * @param  string  $key
   * @return array
   */
  public static function pluck( array $collection, string $key ) : array
  {
    return array_map( function( $v ) use ( $key ) {
      return is_object( $v ) ? $v->$key : $v[ $key ];
    }, $collection );
  }

  /**
   * Trim whitespace from all values, optionally removing empty ones.
   *
   * @access public
   *
   * @param  array $arr
   * @param  bool  $filter_empty Whether to unset empty values
   * @return array
   */
  public static function trim( array $array, $filter_empty = false ) : array
  {
    $array = array_map( 'trim', $array );
    return ( $filter_empty ) ? array_filter( $array ) : $array;
  }

}

array.helpers.php

<?php
/**
 * Helper function for working with arrays.
 */
require "Arr.php";

/**
 * Extend an associative array.
 *
 * Values in $option array overwrite those in $default, but only for keys
 * which are present in $default. All other keys are discarded.
 *
 * @param  array  $default
 * @param  array  $options
 * @return array
 */
if ( ! function_exists( 'array_extend' ) ) :
function array_extend( array $default, array $options ) : array {
  return Arr::extend( $default, $options );
}
endif;

/**
 * Pluck values from a collection of arrays or objects.
 *
 * @param  array   $array
 * @param  string  $key
 * @return array
 */
if ( ! function_exists( 'array_pluck' ) ) :
function array_pluck( array $collection, string $key ) : array {
  return Arr::pluck( $collection, $key );
}
endif;

/**
 * Trim whitespace from all values, optionally removing empty ones.
 *
 * @param  array $arr
 * @param  bool  $filter_empty Whether to unset empty values
 * @return array
 */
if ( ! function_exists( 'array_trim' ) ) :
function array_trim( array $array, $filter_empty = false ) : array {
  return Arr::trim( $array, $filter_empty );
}
endif;