[^а-яА-ЯїЇєЄіІёЁ]
function removeFirstOccurrences(str, value) {
return str.replace(new RegExp('\\b' + value + '\\b'), '');
}
$str = 'https://toster.ru/1234/4321/';
$x = pathinfo($str);
echo $x['basename'], PHP_EOL;
echo basename($x['dirname']);
https://ideone.com/Yp1LK9