PHP regex replace white space by if it is following single letter

Question

I have user defined string (html formated string to be saved and used in web) and need to find a way to replace each white space which is right after a single letter by

Answer 1

preg_replace('/(?<=\b[a-z]) /i', ' ', $s);

The regular expression here performs a positive lookbehind which ensures that the space is preceded by a single letter and a word boundary.