Newbie here,
Is this enough / safe to keep people out of my admin panel?
<?php if (isset($_SESSION["AccountLevelStandard"])) {
echo "<script>location.href='home.php'</script>";
}
Not even remotely. All someone has to do is disable JavaScript and they have full access to the page.
Use an HTTP redirect and exit the PHP script after sending it.
header("Location: home.php");
exit();
You shouldn't redirect people with standard level access, since that won't catch people who aren't logged in at all and so don't have any kind of access.
Test for people who are not admins instead.