Page is white-screening due to weird problem

I have these three functions inside the same class:

public function checkLogin() {
    if(isset($this->getSessionVal())) {
        return true;
    } else {
        return false;
    }

}

public function getSessionVal($type = 'user') {
    return $this->sanitise($_SESSION[$type]);
}

public function sanitise($input) {
    $input = trim($input);

    if (get_magic_quotes_gpc()) {
         $input = stripslashes($input);
    }

    if($this->conn) {
        $input = mysql_real_escape_string($input);  
    }

    $input = strip_tags($input);

    return $input;
}

When I use the above it white-screens and prints nothing, so typically a syntax error, but it's not syntax (Dreamweaver doesn't show up any, and I'm sure it's not. If I change checkLogin to the following:

public function checkLogin() {
    if(isset($_SESSION['user'])) {
        return true;
    } else {
        return false;
    }

}

The sa开发者_开发问答nitise function is fine, I took that out of getSessionVal and it still white-screeened. I'm completely confused, to me it makes no sense so I have someone has an idea (I know I could do it the way it works, but I want to understand why this doesn't work).

Thanks in advance!

---

 if(isset($this->getSessionVal())) {

isset() is a language construct. You can not pass it a function call as a parameter.

Activate error reporting - you should get an error message.

As a workaround, you could e.g. have getSessionVal() return false if the session variable was not set. (That is if false is not a possible value of what you are returning, of course.)

You would then move the isset into getSessionVal() , and test for false in checkLogin().

---

Remove the isset() when calling the other method in the class.

public function checkLogin() {
    if($this->getSessionVal()) {
        return true;
    } else {
        return false;
    }

}