PHP - filter array by keys containing, not containing

keys_containing.php

<?php
/**
 * Return array with only keys containing a string
 *
 * @param  string $str String to filter keys by.
 * @param  array  $arr Source array.
 * @return array Filtered array.
 */
function keys_containing( $str, $arr ) {
  return array_filter(
    $arr,
    function( $key ) use ( $str ) {
      return strpos( $key, $str ) !== false;
    },
    ARRAY_FILTER_USE_KEY
  );
}

/**
 * Return array without keys containing a string
 *
 * @param  string $str String to filter keys by.
 * @param  array  $arr Source array.
 * @return array Filtered array.
 */
function keys_not_containing( $str, $arr ) {
  return array_filter(
    $arr,
    function( $key ) use ( $str ) {
      return strpos( $key, $str ) === false;
    },
    ARRAY_FILTER_USE_KEY
  );
}