Как вывести переменную из if?

session_start();

	$db = mysqli_connect('localhost', 'root', '', 'register');
	

	$name = $_SESSION['name'];
	$password = $_SESSION['password'];


	
	$select = $_POST['his-wal'];
	$con = mysqli_query($db, "SELECT * FROM users WHERE name='$name' ");
	$row = mysqli_fetch_array($con);
	$get_btc = $row['btc'];
	$get_eth = $row['eth'];
	$get_bch = $row['bch'];

	if(isset($_POST['transfer_to'])){
		
		$amount = $_POST['history-amount'];
		$amount_com = $_POST['history-comission'];
		$addres = $_POST['history-address'];
		

		if($select == 1)
		{
			$dif = $get_btc - $amount_com;
		}
		elseif ($select == 2) 
		{
			echo $get_eth;
		}
		elseif($select == 3)
		{
			echo $get_bch;
		}
		
	}

<input type="text" id="history-address" class="form-control fields-item" name="history-address" value="<?php echo $dif; ?>" style="text-align: left;">