Thanks for the further detail. The error message appeared in the browser (Chrome). Hadn’t looked in the log, but the following appears in the log, which seems to indicate actual issue as a call at line 144 of install.php (as you said, the first warning message is to be expected and not fatal).
[Tue Feb 18 22:29:56.397850 2014] [:error] [pid 780:tid 1480] [client 127.0.0.1:55275] PHP Warning: file_get_contents(http://127.0.0.1:8080/vs): failed to open stream: No connection could be made because the target machine actively refused it.rn in C:\wamp\www\sprinklers\install.php on line 108, referer: http://127.0.0.1/
[Tue Feb 18 22:29:56.398850 2014] [:error] [pid 780:tid 1480] [client 127.0.0.1:55275] PHP Stack trace:, referer: http://127.0.0.1/
[Tue Feb 18 22:29:56.398850 2014] [:error] [pid 780:tid 1480] [client 127.0.0.1:55275] PHP 1. {main}() C:\wamp\www\sprinklers\install.php:0, referer: http://127.0.0.1/
[Tue Feb 18 22:29:56.398850 2014] [:error] [pid 780:tid 1480] [client 127.0.0.1:55275] PHP 2. isValidUrl() C:\wamp\www\sprinklers\install.php:19, referer: http://127.0.0.1/
[Tue Feb 18 22:29:56.398850 2014] [:error] [pid 780:tid 1480] [client 127.0.0.1:55275] PHP 3. file_get_contents() C:\wamp\www\sprinklers\install.php:108, referer: http://127.0.0.1/
[Tue Feb 18 22:29:56.398850 2014] [:error] [pid 780:tid 1480] [client 127.0.0.1:55275] PHP Fatal error: Call to undefined function _() in C:\wamp\www\sprinklers\install.php on line 144, referer: http://127.0.0.1/
[Tue Feb 18 22:29:56.398850 2014] [:error] [pid 780:tid 1480] [client 127.0.0.1:55275] PHP Stack trace:, referer: http://127.0.0.1/
[Tue Feb 18 22:29:56.398850 2014] [:error] [pid 780:tid 1480] [client 127.0.0.1:55275] PHP 1. {main}() C:\wamp\www\sprinklers\install.php:0, referer: http://127.0.0.1/