[FIXED] How to replace in PHP all matches of a digit plus a space with comma in a string

Issue

$str = "Hello 1234567 Stack 56789 Overflow 12345";

$str = preg_replace('/([0-9] )/', ',', $str);

I want this "Hello 1234567, Stack 56789, Overflow 12345,..."

Solution

Use

preg_replace('/\d(?=\s)/', '$0,', $str)

See proof.

Expression explanation

--------------------------------------------------------------------------------
  \d                       digits (0-9)
--------------------------------------------------------------------------------
  (?=                      look ahead to see if there is:
--------------------------------------------------------------------------------
    \s                       whitespace (\n, \r, \t, \f, and " ")
--------------------------------------------------------------------------------
  )                        end of look-ahead

Answered By - Ryszard Czech

Answer Checked By - Mary Flores (PHPFixing Volunteer)