SQL - Like *SOLVED*

I've got a search feature to search for all User Names simialr to what is entered as the search criteria.

I have two users (Joe, John) and when I enter 'Jo' as the search criteria I would expect both Joe and John to be found but I don't get any results. I think my SQL statement is correct but even if I put in John or Joe I still get no results?? Could someone have a look for me.

Thanks.

PHP Code:

---

//This is my query
$query = "SELECT * FROM user_details WHERE user_name LIKE '$username*'";
$result = mysql_query($query);

//Check for matches
if (mysql_num_rows($result) == 0) {

echo "There were no users found with the user name entered";
exit;
} 


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EDIT: I substituted * for % and everything works fine :)