Question

Is this how you would pass a value (“username” in example below) to a custom exception? The question being Would I use __construct()? Is using a custom exception for checking whether an important variable is set an overkill?

class customException extends Exception {

    public function __construct($e) {
        parent::__construct($e); // makes sure variable is set? [1]
        $this->e = $e;
    }
    public function redirect_user() {
        if($this->e === "username") {
            header("Location: ");
        }
    }
}

class testing {

    public function test() {
        try {
            if(!isset($_POST['username'])) {
                throw new customException("username");
            }
        }
        catch(customException $e) {
            $e->redirect_user();
        }
    }
}

[1] http://php.net/manual/en/language.exceptions.extending.php#example-266

On a side note, what’s the purpose of parent::__construct($e)? Wouldn’t that be redundant?

Answer 1

There is no reason for your constructor at all. I would suggest using $this->getMessage() to access the value you are trying to set to $this->e.

So do something like this:

class customException extends Exception {
    public function redirect_user() {
        if($this->getMessage() === "username") {
            print_r("Header");
        }
    }
}

It is much more straightforward and only extends the functionality of the base class rather than unnecessarily overriding the constructor.

That being said, I personally don’t like the thought of using exceptions to execute application flow logic like you are doing. To me, custom Exceptions are useful to interface with custom logging systems, or to be able to log aspects of your application’s state that are not available via the default Exception class.