Remove empty keys from an array recursively.

pis_array_remove_empty_keys.php

<?php
/**
 * Remove empty keys from an array recursively.
 *
 * @param array   $array      The array to be checked.
 * @param boolean $make_empty If the output is to return as an empty string.
 * @since 1.29
 * @see http://stackoverflow.com/questions/7696548/php-how-to-remove-empty-entries-of-an-array-recursively
 */
function pis_array_remove_empty_keys( $array, $make_empty = false ) {
	if ( ! is_array( $array ) ) {
		return;
	}

	foreach ( $array as $key => $value ) {
		if ( is_array( $value ) ) {
			$array[$key] = pis_array_remove_empty_keys( $array[$key] );
		}
		if ( empty( $array[$key] ) ) {
			unset( $array[$key] );
		}
	}

	if ( empty( $array ) && $make_empty ) {
		$array = '';
	}

	return $array;
}