php to remove header & navigation from Twenty-Eleven child theme

If I’m understanding your intent correctly, I think that’s something I would handle in the header.php file rather than the functions.php file.

<?php
if($post->ID != XX) {
     //code to display nav menu goes here
}
?>

where XX is the ID of the page or post you do not want the menu to appear on. The same basic structure would apply to code for the header image.

Thank you for the response. You are correct when you say it should go into the header.php file but I still do not understand where it should go. Here is a portion of my coding if you could explain a little more:

[Code moderated as per the Forum Rules. Please use the pastebin]

I hope I got this pastebin thing right: https://pastebin.com/MFhiVfpm

For the navigation menu, unless removing it from the layout affects your design, I’d just put it around the entire nav tag (lines 36 through 57 in your pastebin):

<?php if($post->ID != XX): ?>
     <nav id="access" role="navigation">
         ...code truncated for the sake of space
     </nav><!-- #access -->
<?php endif ;?>

If you need the nav tag for layout’s sake, you can just put the if conditional around line 56:

<?php
if($post->ID != XX) {
     wp_nav_menu( array( 'theme_location' => 'primary' ) );
}
?>

If I’m reading your code right, you can remove the header the same way by putting the if conditional around lines 5 through 20 (the hgroup tag).

Thank you so much. You give very good instructions! I do understand this now. ??