PHPのエラー『Fatal Error: Call to a Member Function on Non-object』の解決方法

<?php
$obj = null;
$obj->method(); // Fatal Error: Call to a member function method() on null
?>

<?php
function getObject() {
    return null;
}

$obj = getObject();
$obj->method(); // Fatal Error: Call to a member function method() on null
?>

<?php
class MyClass {
    public function getObject() {
        return null;
    }
}

$obj = new MyClass();
$obj->getObject()->method(); // Fatal Error: Call to a member function method() on null
?>

<?php
class MyClass {
    public static function getObject() {
        return null;
    }
}

$obj = MyClass::getObject();
$obj->method(); // Fatal Error: Call to a member function method() on null
?>

<?php
class MyClass {
    public function __toString() {
        return null;
    }
}

$obj = new MyClass();
$obj->__toString()->method(); // Fatal Error: Call to a member function method() on null
?>

<?php
$closure = function() {
    return null;
};

$obj = $closure();
$obj->method(); // Fatal Error: Call to a member function method() on null
?>

<?php
function callback() {
    return null;
}

$obj = call_user_func('callback');
$obj->method(); // Fatal Error: Call to a member function method() on null
?>

<?php
class MyClass {
    public function __construct() {
        return null;
    }
}

$obj = new MyClass();
$obj->method(); // Fatal Error: Call to a member function method() on null
?>

<?php
class MyClass {
    public static function create() {
        return null;
    }
}

$obj = MyClass::create();
$obj->method(); // Fatal Error: Call to a member function method() on null
?>

<?php
class MyClass implements Iterator {
    public function current() {
        return null;
    }

    public function next() {}
    public function key() {}
    public function valid() {}
    public function rewind() {}
}

$obj = new MyClass();
$obj->current()->method(); // Fatal Error: Call to a member function method() on null
?>

<?php
function generator() {
    yield null;
}

$obj = generator()->current();
$obj->method(); // Fatal Error: Call to a member function method() on null
?>

<?php
class MyClass {
    public function __get($name) {
        return null;
    }
}

$obj = new MyClass();
$obj->property->method(); // Fatal Error: Call to a member function method() on null
?>