Add comma between words

I have a list of about 50 words I want to put comma between each word. Is there a way to do this automatically with PHP?

$addcomma = str_replace(" ",", ",$str);

.... or , if you had an array of words ...


<?php
$words = array( 'yaks' , 'rule' ) ;
//or
$words = file( 'wordlist.txt' ) ;

$wordstr = implode( ',' , $words ) ;
?>