Remove extra spaces but not space between two words

Question

I want to remove extra spaces present in my string. I have tried trim,ltrim,rtrim and others but non of them are working and even tried the below stuffs.

//This removes all the spaces even the space between the words 
// which i want to be kept
$new_string = preg_replace('/\s/u', '', $old_string); 

Is there any solution for this ?

Updated:-

Input String:-

"
Hello Welcome
                             to India    "

Output String:-

"Hello Welcome to India"

Answer 1

$cleanStr = trim(preg_replace('/\s\s+/', ' ', str_replace("\n", " ", $str)));