php mysql ช่วยดู code หน่อยครับมัน insert เข้า database ไม่ได้

<?php
include('inc/config/connect.php');
session_start();
if (isset($_SESSION["Username"])){
    $Username = $_SESSION["Username"];
}
else 
{
    $Username ="";
}

$post = $_PST['post'];
if (!post != "") {
$date_added = date ("Y-m-d");
$added_by = "$Username";
$user_posted_to = "test123";

$sqlCommand = "INSERT INTO post VALUES('', '$post','$date_added', '$added_by', '$user_posted_to')";
$Query = mysql_query($sqlCommand) or die (mysql_error());
mysql_query($sqlCommand) or die(mysql_error());
}
?>