Q: Find the username and password in a request header and sensor it I'm receiving a complete request header from a third party. I need to hide the password and username.
Php-Auth-Pw:     p@ssword
Php-Auth-User:   testuser

How can I make it to look like this
Php-Auth-Pw:     ******
Php-Auth-User:   ******

I don't fully understand regular expressions just yet, and I've just read something about lookbehinds.
I've found this;
(?<=\Php-Auth-Pw:\s)(\w+)
(?<=\Php-Auth-User:\s)(\w+)

But what would be the correct way to do this with the PHP flavor?

A: You may replace them with a single call to preg_replace:
$s = preg_replace('~\bPhp-Auth-(?:Pw|User):\s*\K\S+~', '******', $s);

See the regex demo
Details:


*

*\b - leading word boundary

*Php-Auth- - a literal char sequence Php-Auth-

*(?:Pw|User) - either a Pw or User substring

*: - a colon

*\s* - 0+ whitespaces

*\K - a match reset operator

*\S+ - 1 or more non-whitespace characters

