If checkbox is selected...

Hey all. I am currently using a PayPal IPN script let me give a small background on how 2 parts work. One part takes paypal variables and populates them into the script. It does so by this:

// assign posted variables to local variables
$item_name = $_POST['item_name'];
$item_number = $_POST['item_number'];
$payment_status = $_POST['payment_status'];
$payment_amount = $_POST['mc_gross'];
$payment_currency = $_POST['mc_currency'];
$txn_id = $_POST['txn_id'];
$receiver_email = $_POST['receiver_email'];
$payer_email = $_POST['payer_email'];
$custom = $_POST['custom'];
$payment_date = $_POST['payment_date'];
$invoice = $_POST['invoice'];

I also have to use paypal variables for this. There's a list here:

https://cms.paypal.com/us/cgi-bin/?&cmd=_render-content&content_ID=developer/e_howto_html_Appx_websitestandard_htmlvariables

Okay, onto the help part. I have my IPN script send the user's email address to a text file which I store my mailing list data in. It does so by this:

$File = "..//mailer/data/email.txt";
$Handle = fopen($File, 'a');
$MyData = "\"". $payer_email . "\"" . "," . "\"" . $invoice . "\"" . "," . "\"" . $custom . "\"" . "\r\n";
fwrite($Handle, $MyData);
fclose($Handle);

Basically, I want the user to check a checkbox, and it runs that part of the script. If not, it doesn't. This allows the user to choose to subscribe or not. So I need an if function and I need to somehow see if the checkbox is checked in the IPN script. Here's my form code:

<input type="checkbox" name="os0" value="yes" checked>

Thanks! If you need more information, I can try and assist.

if($_POST['os0'] == "on")

so the total code would look like this:

if($_POST['os0'] == "on") {
$File = "..//mailer/data/email.txt";
$Handle = fopen($File, 'a');
$MyData = "\"". $payer_email . "\"" . "," . "\"" . $invoice . "\"" . "," . "\"" . $custom . "\"" . "\r\n";
fwrite($Handle, $MyData);
fclose($Handle);
}

And if the checkbox wasn't checked, it would not run that piece of code?

Correct

And this is the correct form checkbox:

<input type="checkbox" name="os0" checked>

Most browsers will accept it, but if you want to keep strict rules, you cannot have an option without a value, therefore you have to write:


<input type="checkbox" name="os0" checked="checked">


In addition any tag requires an end, but there is no </input>, therefore by strict rules it reads


<input type="checkbox" name="os0" checked="checked" />

Ok, and in the PHP part, does "on" mean the same thing as checked?

Yes, in HTML it is "checked", PHP receives it as "on", both meaning the same thing.
Only the counterpart doesn´t exist in PHP, in HTML "unchecked" will arrive in PHP as
$_POST['os0'] == "";

In fact, the form submits checkbox and radio inputs only if they are checked/selected. Thus, the best way to check the presence of a checkbox's value (or any other input element) in a page is using isset().
if(isset($_POST['os0']))
Otherwise, you'll get "unknown index" warning when you execute your code in a STRICT error_reporting environment.