รบกวนพี่ๆช่วยแปลความหมายคำสั่ง เป็นคำสั่งที่ไม่ค่อยคุ้น ให้หน่อยค่ะ php กับ mysql

$page_name = 'profile';
include("connect.php");
$user = $_GET[username];
$sql5 = mysql_query("SELECT * FROM members where username = '$user'") or die(mysql_error());
$myrow = mysql_fetch_array($sql5);
$username = $myrow['username'];
if((!$username) == 1){header('Location: index.php');}
$result = mysql_query("SELECT * FROM sitesettings");
while($myrow = mysql_fetch_array($result))
{
$title = "".$myrow["domain"]." - Profile: $user";
$rpp = 10; // results per page
$adjacents = 4;
$page = intval($_GET["page"]);
if(!$page) $page = 1;
$siteurl = $myrow["site_url"];
$reload = "".$myrow["site_url"]."/profile-".$user."";
}