How can I find the version of php that is running on a distinct domain name?

I use redbot, a great tool to see the PHP version, but also many other useful infos like headers, encoding, keepalive and many more.

Try it on

http://redbot.org

I love it!

I also up vote Neil's answer: curl -I http://websitename.com

Sometimes, PHP will emit a X-Powered-By: response header which you can look at e.g. using Firebug.

If this setting (controlled by the ini setting expose_php) is turned off (it often is), there is no way to tell the PHP version used - and rightly so. What PHP version is running is none of the outside world's business, and it's good to obscure this from a security perspective.

This works for me:

curl -I http://websitename.com

Which shows results like this or similar including the PHP version:

HTTP/1.1 200 OK
Date: Thu, 13 Feb 2014 03:40:38 GMT
Server: Apache
X-Powered-By: PHP/5.4.19
P3P: CP="NOI ADM DEV PSAi COM NAV OUR OTRo STP IND DEM"
Cache-Control: no-cache
Pragma: no-cache
Set-Cookie: 7b79f6f1623da03a40d003a755f75b3f=87280696a01afebb062b319cacd3a6a9; path=/
Content-Type: text/html; charset=utf-8

Note that if you receive this message:

HTTP/1.1 301 Moved Permanently

You may need to curl the www version of the website instead i.e.:

curl -I http://www.websitename.com