列出来自id [duplicate]的数据库中的所有用户名

I want to list all username from database if the id exists. That code works fine in database select * from users where id IN (1,2,3,4,5).

But in php it doesn't work. My php code is

$sql = "select * from users where id IN (1,2,3,4,5)"; 
$result = mysql_query($sql); 
if ( mysql_num_rows($result) > 0 ) { 
  $row = mysql_fetch_assoc( $result );
  echo $row["username"]; 
}

This php code only list one user name. I want to list all usernames. Sorry for my bad English. Thanks.

</div>

<?php
$sql = "select * from users where id IN (1,2,3,4,5)"; 
$result = mysql_query($sql); 
if ( mysql_num_rows($result) > 0 ) {
    while($row = mysql_fetch_assoc( $result )) {
        echo $row["username"]."
";
    } 
}

if you only fetch once, you will only get one row - obviously. so if you want all rows, you have to fetch as long as there are rows to fetch.