Modify Several PHP files

# Needed a script to loop through several php files modify any links, and insert some code into the header of each page.
# Since the header was standard on each page, it was easy enough to match, as were any links
# My question: How could I refactor this to be more efficient than using two different sub/gsubs, and a seperate file write?

Dir.glob('*.php') do |file_name| 
  
  #Find one instance of the header, and modify it
  content = File.read(file_name).sub(/regex/i, "multiline\nreplacement")

  #find every instance of <a href="blah.php"> and modify it to say <a href="blah.php?foo=bar">
  content.gsub!(/regex/i,'replacement')

  #write the modified contents to a new file with the same name
  file = File.open(file_name, 'w') { |file| file.puts content }
end