Problem mit, ehm keine Ahnung ^^. .. PHP ?

<tr>
	<td width="10%">
	<input type="text" name="benutzer_name" class="form-control" placeholder="Benutzer suchen..."><br>
	<?php
	$user_name=$_GET['benutzer_name'];
	$queryfrom = "SELECT id FROM users WHERE username=$user_name"; 
	$resultate = mysql_query($queryfrom); 
	$userid=-1;
	if(!mysql_num_rows($resultate))
	{
		$userid=-1; 
	}
	else
	{
		$userid=$resultate;
	}
	echo "<form action=viewuser.php?id=$userid method='post'>";
	?>					
	<button class="btn btn-lg btn-primary btn-block" type="submit">Suchen</button>
	</td>
</tr>

<form action="index.php" method="GET">
<input type="text" name="benutzer_name" class="form-control" placeholder="Benutzer suchen..."><input type="submit" value="suche" name="search">
</form>


<?php
if(isset($_GET['search']))
{
PHP CODE
}
?>

<br><input type="text" name="benutzernamebyid" class="form-control" placeholder="Benutzer suchen..."><br>
<?php
	$namebyid = $_GET['benutzernamebyid'];
	$queryfrom = "SELECT id FROM users WHERE username='$namebyid'"; 
	$resultate = mysql_query($queryfrom); 
	if(!mysql_num_rows($resultate))
	{
		$userid=-1;
	}
	else
	{
		$userid=$resultate;
	}
	echo "<form action=viewuser.php?id=$userid method='POST'>";
?>					
<button class="btn btn-lg btn-primary btn-block" type="submit">Suchen</button>