请问php使用mysql_query时遇到的奇怪有关问题

$uid='6';

$result = mysql_query("SELECT * FROM user WHERE uid='$uid'")

    or die("Invalid query: " . mysql_error());

print_r(fetch_array($result));

$username='匿名';

$resultt = mysql_query("SELECT * FROM user WHERE username='$username'")

    or die("Invalid query: " . mysql_error());

print_r(fetch_array($resultt));

echo $resultt = mysql_query("SELECT * FROM user WHERE username='$username'")    or die("Invalid query: " . mysql_error());