My TRUNCATE statements DO NOT WORK.

[Gordon White]

Ii have the following code that to me looks correct.
But it doesn't work.

<?PHP
include "config.php";

$sql = "TRUNCATE TABLE data1";
$sql.= "TRUNCATE TABLE data2";
$sql.= "TRUNCATE TABLE data3";
$sql.= "TRUNCATE TABLE data4";
$$result = mysqli_query($sql,$conn);

There's lots of stuff following but not necessary.

What is wrong?