how to replace word that contains only special characters from string using regular expression

Question

I have a string and I need to search and replace such a words that contain only special characters in it. no, any other letter eg( @@#$$ , %^&%%$ , &(){}":?? ).

Answer 1

Function

function clean($string) {
   $string = str_replace(' ', '-', $string); // Replaces all spaces with hyphens.
   $string = preg_replace('/[^A-Za-z0-9\-]/', '', $string); // Removes special chars.

   return preg_replace('/-+/', '-', $string); // Replaces multiple hyphens with single one.
}

Usage:

echo clean('a|"bc!@£de^&$f g');

code link

Answer 2

I assume that "words" that only contain special characters are chunks of non-whitespace symbols that are not word characters (letters/digits/underscore).

That means you may split the string with whitespaces (with preg_split('~\\s+~', $s) ), get rid of all chunks that only consist of non-word chars (with preg_grep('~^\\W+$~', $arr, PREG_GREP_INVERT) ), and then join the chunks with a space:

$s = "''' Dec 2016, ?!$%^ End '''";
$result = implode(" ", preg_grep('~^\W+$~', preg_split('~\s+~', $s), PREG_GREP_INVERT));
echo $result;

See the PHP demo