Often when you are busting a directory for common files, you can identify scripts (for example test.php) that look like they need to be passed an unknown parameter. This hopefully can help find them.
The -off flag allows you to specify an offset (helps with dynamic pages) so for example, if you were getting alternating response sizes of 4444 and 4448, set the offset to 5 and it will only show the stuff outside the norm
Adding new params from source
The following regexes might be useful to parse $_GET or $_POST parameters from source:$> grep -rioP '$_POST[\s*["']\s*\w+\s*["']\s*]' PHPSOURCE | grep -oP '$_POST[\s*["']\s*\w+\s*["']\s*]' | sed -e "s/$_POST[\s*["']//g" -e "s/\s*['"]\s*]//g" | sort -u > /tmp/outfile.txt
$> grep -rioP '$_GET[\s*["']\s*\w+\s*["']\s*]' PHPSOURCE | grep -oP '$_GET[\s*["']\s*\w+\s*["']\s*]' | sed -e "s/$_GET[\s*["']//g" -e "s/\s*['"]\s*]//g" | sort -u > /tmp/outfile.txt
