What is wrong with this PHP regular expression?

$output = preg_replace("|(/D)(/s+)(/d+)(;)|", "//1,//3;", $output);

I'm trying to replace all alphabetical character followed by one or more whitespace characters (tabs and/or spaces) followed by one or more numerical characters followed by a semicolon with the alphabetical character followed by a comma followed by the numerical digits and then the semicolon.

I'll provide an example:

Start:

hello world      1007;

End:

hello world,1007;

From stackoverflow Thomas Owens

• Should those forward-slashes be backslashes? You'll need to escape them for PHP too unless you change your double-quotes to single-quotes.

  From Ted Percival

• The two '|' at the start and end probably are incorrect - and should both be forward-slashes.

  All other forward slashes should be backward slashes (and need escaping).

  And since PHP 4.04 $n is the preferred way of referring to a capture group.

  $output = preg_replace("/(\\D)\\s+(\\d+;)/", "$1,$2", $output);
  

  If you use single quotes you don't need to escape your backslashes:

  $output = preg_replace('/(\D)\s+(\d+;)/', '$1,$2', $output);
  

  Ted Percival : If I recall correctly, the start- and end-of-pattern symbols (the '|'s) are required in the PHP preg_* functions.

  samjudson : Good point - I also forgot to escape my back slashes.
  From samjudson

• I'm not in a programming mindset today...that was the fifth stupid, idiotic thing I've done this morning, and I've only been at work for 2 hours.

  From Thomas Owens

• You want backslashes in the regular expression, not forward slashes. The starting and ending pipes are needed (or another delimiter for the regex)

  $x = "hello world      1007;";    
  echo preg_replace('|(\D)(\s+)(\d+)(;)|','$1,$3',$x);
  echo preg_replace('/(\D)(\s+)(\d+)(;)/','$1,$3',$x);
  echo preg_replace('{(\D)(\s+)(\d+)(;)}','$1,$3',$x);
  

  samjudson : I didn't know you could use anything for the start and end delimiters, thanks.
  From Alan Storm