PHP - Search for Mastodon usernames and replace with links

<?php
function mastodonUsers($text) {
    return preg_replace_callback(
        '~
        (?<=
            ^
            |
            (?<=
                [^a-zA-Z0-9-.&;/]
            )
        )
        (?(?=
                <a\b[^>]*>.+?</a>|<[^>]*>
            )
            (?:
                <a\b[^>]*>.+?</a>|<[^>]*>
            )
            |
            (?<name>
                [@]{1}[A-Za-z_\p{L}]+[A-Za-z0-9_\p{L}]+
            )
        )
        (?<domain>
            [@]{1}[A-Z0-9.-]+\.[A-Z]{2,}
        )\b
        ~uxsi',

        function($matches) {
            if (isset($matches['name']) && isset($matches['domain'])) {
                return '<a href="https://' . $matches['domain'] . '/' . $matches['name'] . '">' . $matches[0] . '</a>';
            } else {
                return $matches[0];
            }
        },
        $text
    );
?>