Question

I’m writing a WordPress plugin, and one of the features is removing duplicate whitespace.

My code looks like this:

return preg_replace('/\s\s+/u', ' ', $text, -1, $count);

• I don’t understand why I need the u
  modifier. I’ve seen other plugins
  that use preg_replace and don’t
  need to modify it for Unicode. I
  believe I have a default installation
  of WordPress .

• Without the modifier, the code
  replaces all the spaces with Unicode
  replacement glyphs instead of spaces.

• With the u modifier, I don’t get
  the glyphs, and it doesn’t replace all the whitespace.

Each space below has from 1-10 spaces. The regex only removes on space from each group.

Before:

This sentence  has extra space.  This doesn’t.  Extra  space, Lots          of extra space.

After:

This sentence has extra space. This doesn’t. Extra space, Lots         of extra space.

$count = 9

How can I make the regex replace the whole match with the one space?

---

Update: If I try this with regular php, it works fine

$new_text = preg_replace('/\s\s+/', ' ', $text, -1, $count);

It only breaks when I use it within the wordpress plugin.
I’m using this function in a filter:

function jje_test( $text ) {
    $new_text = preg_replace('/\s\s+/', ' ', $text, -1, $count);
    echo "Count: $count";
    return $new_text;
}

add_filter('the_content', 'jje_test');

I have tried:

• Removing all other filters on the_content
  remove_all_filters('the_content');
• Changing the priority of the filter added to the_content, earlier or later
• All kinds of permutations of \s+, \s\s+, [ ]+ etc.
• Even replacing all single spaces with an empty string, will not replace the spaces

Answer 1

This will replace all sequences of two or more spaces, tabs, and/or line breaks with a single space:

return preg_replace('/[\p{Z}\s]{2,}/u', ' ', $text);

You need the /u flag if $text holds text encoded as UTF-8. Even if there are no Unicode characters in your regex, PCRE has to interpret $text correctly.

I added \p{Z} to the character class because PCRE only matches ASCII characters when using shorthands such as \s, even when using /u. Adding \p{Z} makes sure all Unicode whitespace is matched. There might be other spaces such as non-breaking spaces in your string.

I’m not sure if using echo in a WordPress filter is a good idea.