Remove all spaces but leave 1 space each

[joon1]

$word="01 2  3   4    5     6      7        8         9          0'; 

I have a variable like the above.
and I like to remove all spaces between the numbers but leave 1 space between numbers if each has any space.
The following is the code I tried, but failed

$word = str_replace( ' ', ' ', $word ); $word = str_replace( ' ', ' ', $word ); $word = str_replace( ' ', ' ', $word );

it is still remained many spaces which is more than one space .

The result below is what I want.

01 2 3 4 5 6 7 8 9 0

[Dormilich]

http://php.net/preg-replace

[John_Betong]

@joon1

$word = str_replace( ’ ', ’ ', $word );

As a test, try replacing the single space to be replaced with ‘X’ then echo the result.

Repeat until there are only single spaces and X showing.

From the echoed results a solution should be available.

[chorn]

oKhhZ - created on 3v4l.org

[Gandalf]

while ( strstr($word, '  ') )
  $word = str_replace('  ', ' ', $word);

[davidtsadler]

$word = preg_replace('/\s+/', ' ', $word);