为什么这个PHP if语句仍包含内容？

I want parts/lesson-links.php not to be included when get_the_lesson_contenttype() equals to "Hint" or "Main Lesson".

So I did this:

  <h2><?php echo get_the_lesson_contenttype(); ?></h2>

  <?php if (get_the_lesson_contenttype() != 'Hints' || get_the_lesson_contenttype() != 'Main Lesson') { ?>
    <?php 
      include( locate_template( 'parts/lesson-links.php' ) );
    ?>
  <?php } ?>

But as you can see in this page: http://clo2015.chineselearnonline.com/lessoncontent/lesson-004-hints-and-tips/

parts/lesson-links.php is still being added. What did I do wrong?

EDIT:

Strangely it works without the ||, only adding Hint:

  <?php if (get_the_lesson_contenttype() != 'Hints') include( locate_template( 'parts/lesson-links.php' ) );?>

You mixed up your ANDS or ORS (pun intended (I'm not funny))

<h2>
    <?php echo get_the_lesson_contenttype(); ?>
</h2>

<?php 
    if (get_the_lesson_contenttype() != 'Hints' && get_the_lesson_contenttype() != 'Main Lesson') {
        include( locate_template( 'parts/lesson-links.php' ) );
    }
?>

Lets take a look at some boolean operations! Here we gooooo.....

You said...

I want parts/lesson-links.php not to be included when get_the_lesson_contenttype() equals to "Hint" or "Main Lesson".

Well thats like...

if (get_the_lesson_contenttype() == "Hint" || get_the_lesson_contenttype() == "Main Lesson")
    DONT INCLUDE

ACTIVATE NEGATION!!!!!!! (Basically flip EVERYTHING!)

if (get_the_lesson_contenttype() != "Hint" && get_the_lesson_contenttype() != "Main Lesson")
    DOOOO INCLUDE