Add character after each word

Add character after each word

How can I implode character after each word?
I have tried the following:
$query = implode("* ", preg_split("/[\s]+/", $query));
but it always ignores one word. for example: test test will give me test*
test, test will give me test, test test test test will give me test* test*
test* test
Also tried $query = implode("*", str_split($query)); but it gives me
gibberish if query is in Cyrillic characters.