PHP Fatal error: Using $this when not in object context

Question

I've got a problem:

I'm writing a new WebApp without a Framework.

In my index.php I'm using: require_once('load.php');

And in load.php I'm using require_once('class.php'); to load my class.php.

In my class.php I've got this error:

Fatal error: Using $this when not in object context in class.php on line ... (in this example it would be 11)

An example how my class.php is written:

class foobar {

    public $foo;

    public function __construct() {
        global $foo;

        $this->foo = $foo;
    }

    public function foobarfunc() {
        return $this->foo();
    }

    public function foo() {
        return $this->foo;
    }
}

In my index.php I'm loading maybe foobarfunc() like this:

foobar::foobarfunc();

but can also be

$foobar = new foobar;
$foobar->foobarfunc();

Why is the error coming?

Answer 1

In my index.php I'm loading maybe foobarfunc() like this:

 foobar::foobarfunc();  // Wrong, it is not static method

but can also be

$foobar = new foobar;  // correct
$foobar->foobarfunc();

You can not invoke the method this way because it is not a static method.

foobar::foobarfunc();

You should instead use:

$foobar->foobarfunc();

If however, you have created a static method something like:

static $foo; // your top variable set as static

public static function foobarfunc() {
    return self::$foo;
}

then you can use this:

foobar::foobarfunc();