A simple snippet to remove trailing numbers at the end of wordpress urls. For example: redirect http://example.com/foobar/2024/ to http://example.com/foobar/. Don't use it if your permalink structure ends with "%post_id%"! This will return an infinite redirect-loop!

redirect.php

<?php

// get the url
$url = 'http://' . $_SERVER[HTTP_HOST] . $_SERVER[REQUEST_URI];

// check if there are any slashes inside the url string
if (strpos($url, '/')) {

	// split the string in pieces
	// use "/" as separator
	$url_pieces = split('/', $url);

	// we need the index of the last piece to check if it contains numbers ...
	// ... but we have to substract 1 cause an array starts with 0 ...
	// ... and we have to substract another 1: the last piece is empty because urls have a trailing "/" and we are using "/" as seperator
	$last_index = count($url_pieces) - 2;
	
	// get the last piece
	$last_url_piece = $url_pieces[$last_index];
	
	// check if the last piece contains only numbers
	if (preg_match('/^[0-9]*$/', $last_url_piece)) {
	
		// get the correct canonical url
		$new_url = get_permalink($post->ID);	

		// redirect via 301 redirection
		wp_redirect($new_url, 301);
	}
}

?>