Warning: mysql_fetch_array(): supplied argument is not a valid MySQL result resource in

<?
	mysql_connect('localhost','root','0815');
	mysql_select_db("Cyber") or die("Select Database Error"); 
	
	if(trim($_POST["login_username"]) == "")
	{
		echo "Please input Username!";
		exit();	
	}
	
	if(trim($_POST["login_password"]) == "")
	{
		echo "Please input Password!";
		exit();	
	}	
		
	if($_POST["login_password"] != $_POST["txtConPassword"])
	{
		echo "Password not Match!";
		exit();
	}
	
	if(trim($_POST["name_user"]) == "")
	{
		echo "Please input Name!";
		exit();	
	}	
	
	$strSQL = "SELECT * FROM members WHERE login_username = '".trim($_POST['login_username'])."' ";
	
	$objQuery = mysql_query($strSQL) or die(mysql_error()); 
	$objresult = mysql_fetch_array($objquery);

	
	
	if($objResult)
	{
			echo "Username already exists!";
	}
	else
	{	
		
		$strSQL = "INSERT INTO members (login_username,login_password,name_user) VALUES ('".$_POST["login_username"]."', 
		'".$_POST["login_password"]."','".$_POST["name_user"]."')";
		$objQuery = mysql_query($strSQL);
		
		echo "Register Completed!<br>";		
	
		echo "<br> Go to <a href='index.php'>Login page</a>";
		
	}

	mysql_close();
?>