my php username line is not checking if the username already exist in my db : i used this line of code to check if the username already exist in my database 
if the user does not exist it creates it if it does echo 'username alrady exist'


			if(!DB::query('SELECT username FROM users WHERE username=:username', array(':username'=>$username))){

				//create user
			DB::query('INSERT INTO users VALUES (null, :username, :password, :email)', array(':username'=>$username, ':password'=>password_hash($password, PASSWORD_BCRYPT), ':email'=>$email));
			echo "SUCCESS!";

	}ELSE{
		echo 'USER ALREADY EXIST';
	}
	} 