Search the entire file system for files with the extension ".php" and for each file found, execute the command "sed" to search for lines beginning with "<? " and swap the order of the text on the line so that the text after "<? " is printed first, followed by "<? ".
find / -name "*.php" | xargs sed -n 's/\(^<\? *\)\(.*\)/\2 \1/gp'