RewriteEngine On

# /refer/SCH1234  ->  refer.php?code=SCH1234
RewriteRule ^refer/([A-Za-z0-9]{4,20})/?$ refer.php?code=$1 [L,QSA]

# /.well-known/assetlinks.json must be served as-is with correct content type
<FilesMatch "assetlinks\.json$">
    Header set Content-Type "application/json"
</FilesMatch>
