[Php] Unknown column 'Admin' in 'where clause'

	$standard	= array("home","crew","news","services","incidents","contact");
	$admin 		= array("add_news","change_news","delete_news","view_news");
	$member		= array("view_news");
	
	$query 	= mysql_query("SELECT us_rank FROM users WHERE us_username = ".$_SESSION['username']) or die(mysql_error());
	$result = mysql_fetch_assoc($query);
	$rank 	= $result['us_rank'];
	
	if(isset($_GET['page']))
	{
		$pages = $standard;
		
		if(isset($rank))
		{
			$rank = strtolower($rank);
			
			if(isset($$rank))
			{
				$pages = array_merge($standard, $$rank);
			}
		}
		if(in_array($_GET['page'], $pages))
		{
			if(file_exists($_GET['page'].'.php'))
			{
				include $_GET['page'].'.php';
			}
			else
			{
				echo('<p class="error">Ongeldige pagina opgegeven.</p>');
			}
		}
		else
		{
			echo('<p class="error">Ongeldige pagina opgegeven.</p>');
		}
	}

$standard	= array("home","crew","news","services","incidents","contact");
	$admin 		= array("add_news","change_news","delete_news","view_news");
	$member		= array("view_news");
 
	$query 	= mysql_query("SELECT us_rank FROM users WHERE us_username = ".$_SESSION['username']) or die(mysql_error());
	$result = mysql_fetch_assoc($query);
	$rank 	= $result['us_rank'];
 
	if(isset($_GET['page']))
	{
		$pages = $standard;
 
		if(isset($rank))
		{
			$rank = strtolower($rank);
 
			if(isset($$rank))
			{
				$pages = array_merge($standard, $$rank);
			}
		}
		if(in_array($_GET['page'], $pages))
		{
			if(file_exists($_GET['page'].'.php'))
			{
				include $_GET['page'].'.php';
			}
			else
			{
				echo('<p class="error">Ongeldige pagina opgegeven.</p>');
			}
		}
		else
		{
			echo('<p class="error">Ongeldige pagina opgegeven.</p>');
		}
	}

mysql_query("SELECT us_rank FROM users WHERE us_username = ".$_SESSION['username'])

mysql_query("SELECT us_rank FROM users WHERE us_username = ".$_SESSION['username'])

mysql_query("SELECT us_rank FROM users WHERE us_username = '".$_SESSION['username'] . "'")

mysql_query("SELECT us_rank FROM users WHERE us_username = '".$_SESSION['username'] . "'")

<?php
$query     = mysql_query("SELECT us_rank FROM users WHERE us_username = ".$_SESSION['username']) or die(mysql_error());
?>

<?php
$query     = mysql_query("SELECT us_rank FROM users WHERE us_username = ".$_SESSION['username']) or die(mysql_error());
?>

<?php
$query     = mysql_query("SELECT us_rank FROM users WHERE us_username = '".$_SESSION['username']."'") or die(mysql_error());
?>

<?php
$query     = mysql_query("SELECT us_rank FROM users WHERE us_username = '".$_SESSION['username']."'") or die(mysql_error());
?>