preg_replace inside of preg_match_all problems

[Exiled]

I'm trying to find some certain blocks in my data file and replace something inside of them. After that put the whole thing (with replaced data) into a new file. My code at the moment looks like this:\[code\]$content = file_get_contents('file.ext', true);//find certain pattern blocks firstpreg_match_all('/regexp/su', $content, $matches);foreach ($matches[0] as $match) { //replace data inside of those blocks preg_replace('/regexp2/su', 'replacement', $match);}file_put_contents('new_file.ext', return_whole_thing?);\[/code\]Now the problem is I don't know how to return_whole_thing. Basically, file.ext and new_file.ext are almost the same except of the replaced data.Any suggestion what should be on place of \[code\]return_whole_thing\[/code\]?Thank you!