Redirect from 404

redirect-404.php

<?php

function pm_redirect_posts_from_404() {
	global $wp, $wpdb, $wp_query, $pm_query;

	if(is_404()) {
		$slug = basename($wp->request);

		$element = $wpdb->get_row($wpdb->prepare("
			SELECT * FROM {$wpdb->posts}
			WHERE post_name = %s
			AND post_status = 'publish'
			",
			$slug
		));

		if(!empty($element->ID)) {
			$url = get_permalink($element->ID);
		} /*else {
			$element = $wpdb->get_row($wpdb->prepare("
				SELECT * FROM {$wpdb->terms}
				LEFT JOIN {$wpdb->term_taxonomy} ON {$wpdb->terms}.term_id = {$wpdb->term_taxonomy}.term_id
				WHERE slug = %s",
				$slug
			));

			if(!empty($element->term_id)) {
				$url = get_term_link((int) $element->term_id, $element->taxonomy);
			}
		} */

		if(!empty($url)) {
			wp_safe_redirect($url, 301);
			exit();
		}
	}
}
add_action('template_redirect', 'pm_redirect_posts_from_404', 1);