So here is a cool trick I didn’t know about before. Ever wanted to know if a site you’re looking at was built using PHP?
Just append this query string to the URL of the site in question, and if you see the PHP logo you’ll know you’ve hit the jackpot.
Of course it’s probably easier to just inspect the page headers to see what the site is using. With the added benefit of knowing exactly which version of PHP the site is running as well. Not to mention it is probably easier than trying to remember the crazy PHP UID string above.
Finally, this doesn’t work in all cases. It is possible to configure PHP to suppress both the X-Powered-By headers, and the use of the UID String by setting the following directives in your php.ini file.
And if you’re really curious, you can find this and a few other UID strings check out the PHP source file ext/standard/info.h