Undefined iindex and password decryption!!

[gasoga]

Hi i have created a login form and want to check the details against whats in the database!
When entering the password i encrypted it so in order to chexk it i need to decrypt it the code im using to this give me the error:

PHP Notice: Use of undefined constant Password - assumed 'Password' PHP Notice: Undefined index: SubPass

the code is:

$db = odbc_connect($dbsource, $dbuser, $dbpass) or die(odbc_errormsg);
$Q01 = "SELECT Password, ENCRYPT('$POST[Password]') as SubPass
FROM $dbtable
WHERE UserName='$POST[UserName]'";
$R01 = odbc_exec($db,$Q01) or die("Bad Q01:".mysql_error());
odbc_fetch_into($R01, $Info);

if($_POST[Password] != $Info['SubPass'])
	{
	$ErrorCode = "Your Paswword is Incorect";
	//ViewHeader();
	include('home.php');
	//ViewFooter();
	exit;
	}

any help would be much appreciated!!!
thanx!!!

[jpmoriarty]

dont put array's directly into your string - come out of the string first:

$Q01 = "SELECT Password, ENCRYPT('".$POST[Password]."') as SubPass
FROM $dbtable
WHERE UserName='".$POST[UserName]."'";

i'd also point out that most passwords are usually encrypted using one way fucntions, the benefit being of course that you dont need to decrypt it at any stage: you simply encrypt the password that's been entered using the same funciton. If the two encrypted passwords match, then obviuosly their plaintext's matched, and so the password is correct.

[superwormy]

To clarify jpmoriarty 's excellent note on how most passwords are not ever decrypted, most passwords are stored after being md5 hashed, ( www.php.net/md5 ), one way hashing of the password makes sure it'll never be unhashed.