<form method="post" action="">
User Name:  <input type="text" name="username" value="" />
Normaler Name:<input type="text" name="normalname" value="" />
<input type="submit" value="suchen" name="submit">
</form>

$sql = "
SELECT u.id, u.username, c.avatar, u.name, c.hits 
FROM #__users AS u RIGHT JOIN  #__comprofiler AS c 
ON u.id = c.user_id WHERE u.username LIKE '". mysql_real_escape_string($_POST['username']) ."%' 
OR u.name LIKE '". mysql_real_escape_string($_POST['normalname']) ."%'
LIMIT 30
";

SELECT u.id, u.username, c.avatar, u.name, c.hits 
FROM #__users AS u RIGHT JOIN  #__comprofiler AS c 
ON u.id = c.user_id WHERE u.username LIKE '". mysql_real_escape_string($_POST['username']) ."%' 

LIMIT 30
";

OR u.name LIKE '". mysql_real_escape_string($_POST['normalname']) ."%'

Notice: Undefined index: username user-suche.php on line 40

Notice: Undefined index: normalname in user-suche.php on line 41

$sql = "
	SELECT u.id, u.username, c.avatar, u.name, c.hits 
	FROM #__users AS u, #__comprofiler AS c 
	WHERE u.id = c.user_id 	AND (u.username LIKE '". mysql_real_escape_string($_POST['username']) ."%'
	OR u.name LIKE '". mysql_real_escape_string($_POST['normalname']) ."%')
	LIMIT 30
";

$sql = "SELECT u.id, u.username, c.avatar, u.name, c.hits 
	FROM #__users AS u, #__comprofiler AS c 
	WHERE u.id = c.user_id";

if(isset($_POST['username']) || isset($_POST['normalname'])){
  $sql .= " WHERE ";
}

if(isset($_POST['username'])){
  $sql .= " u.username LIKE '". mysql_real_escape_string($_POST['username']) ."%'";
}

if(isset($_POST['username']) && isset($_POST['normalname'])){
  $sql .= " OR ";
}

if(isset($_POST['normalname'])){
  $sql .= "u.name LIKE '". mysql_real_escape_string($_POST['normalname']) ."%'";
}

Invalid argument supplied for foreach() in /user-suche.php on line 69

foreach ($rows as $row) {
	echo renderPhoto($row['id'], $row['username'], $row['avatar'], $row['name'], $row['hits']) . "\n";
}