SQL / PHP if NULL show else - php

Question

We are trying to complete / fix the below code, We cant seem to do the following.
Check if 'Check_Activation' is set to 'NULL' within the Database
IF value is NULL direct the user to one of the forms (1,2,3)
And finally if the 'Check_Activation' has already been activated and isn't 'NULL' prevent user from accessing one of the 3 forms.
I know its basicly there but we can't seem to figure out the final bug.
Please have a quick look at the code below and if anyone notices anything that isn't right please advice us.
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<?php
$username = $_POST['username'];
$activation_code = $_POST['activation_code'];
$activation_codeurl = $activation_code;
$usernameurl = $username;
$db_host = "localhost";
$db_name = "aardvark";
$db_use = "aardvark";
$db_pass = "aardvark";
$con = mysql_connect("localhost", $db_use, $db_pass);
if (!$con){
die('Could not connect: ' . mysql_error());
}
mysql_select_db($db_name, $con);
$checkcustomer = mysql_query("SELECT `Check_Activation` FROM `members` WHERE `Username` = '".$username."' & `Activation` = '".$activation_code."'; ");
$array = mysql_fetch_array($checkcustomer);
if (is_null($array['Check_Activation'])) {
$username = substr($username, 0, 1);
if($username == '1') {
$redirect_url='form-one.php?membernumber='.$usernameurl.'&activation_code='.$activation_codeurl;
} elseif($username == '2') {
$redirect_url='form-two.php?membernumber='.$usernameurl.'&activation_code='.$activation_codeurl;
} elseif($username == '3') {
$redirect_url='form-three.php?membernumber='.$usernameurl.'&activation_code='.$activation_codeurl;
}
header("Location:". $redirect_url);
}
else
{
?>

Answer 1

Try this, You need to fetch the row from table and then you can check the values,
$val = mysql_fetch_array($checkcustomer);
if (is_null($val['Check_Activation']))
instead of
$val = mysql_query($checkcustomer);
if ($val == 'NULL')
NOTE: Use mysqli_* functions or PDO instead of using mysql_* functions(deprecated)

Answer 2

before I get into the technicality of what your are trying to accomplish, I have some advice for your code in general. You should avoid using the mysql api as it is deprecated, and use the mysqli api instead. I think you will also find that it is easier to use.
Now for the code:
You have this line in your code which seems to be incorrect, $checkcustomer is a result set from your previous query, so why are you running it as a query again?
$val = mysql_query($checkcustomer);
You already have the result set so do this:
$array = mysql_fetch_array($checkcustomer);
And then take the value of Check_Aviation;
if (is_null($array['Check_Aviation'])) {
//Do Something
}
Should solve your issue