How To See If A Form Element Was Not Posted

I have a form where e-mail is optional. To control that there is a checkbox. If that checkbox is unchecked, the e-mail textbox would be disabled and therefore not posted on submit.

Solution 1:

if the field "#YourEMail" is optional you can check if exists in PHP. There is no need for enable/disable the field using JS.

if (isset($_POST['submit'])) 
{
    if (isset($_REQUEST['YourEMail']) && !empty($_REQUEST['YourEMail'])){
        $_SESSION["email"] = $_REQUEST['YourEMail'];
    }
}

Solution 2:

You can test it like this using a ternary:

(isset($_REQUEST['YourEMail']) && !empty($_REQUEST['YourEMail'])) ? $_SESSION["email"] = $_REQUEST['YourEMail'] : FALSE;

This would only set the session variable if the request variable is set.