replace all combinations of non-alphanumeric characters

Question

I need to to create url from various strings.
So trying to replace all non-alphanumeric characters and all of their combinations - with a hyphen character (-)

$string = "blue - sky";
$string = preg_replace("/[^A-Za-z0-9 ]/", '-', $string);
echo $string;  

result - blue---sky
expected - blue-sky.

Answer 1

use the + sign to replace more than one character with one replacement character:

string = preg_replace("/[^A-Za-z0-9]+/", '-', $string);