WP Redirects

wp-redirect.php

function wp_redirects(){
	$redirects = array(
		'/old/' => '/new/'
	);
	$protocol = isset( $_SERVER['HTTPS'] ) ? 'https://' : 'http://';
	$site_url = str_replace( $protocol, '', get_site_url() );
	$url = str_replace( $site_url, '', $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'] );
	$redirect = $redirects[ $url ];
	if( isset( $redirect )){
		$redirect = $protocol . $site_url . $redirect;
		wp_redirect( $redirect, 301 );
		exit;
	}else{
		global $wp_query;
		$wp_query->set_404();
		status_header( 404 );
	}
}
add_action( 'init', 'wp_redirects', 100 );