WordPress shortcode for conditionally showing content based on whether or not it is an AMP response.

is-amp-endpoint-shortcode.php

<?php
/**
 * Plugin Name: AMP is_amp_endpoint shortcode
 * Description: Add a shortcode for conditionally showing content based on whether or not it is an AMP response.
 * Plugin URI: https://gist.github.com/westonruter/95da1a34dd4a758e6622c6319c54a60b
 * Author Name: Weston Ruter
 * Author URI: https://weston.ruter.net/
 * Gist Plugin URI: https://gist.github.com/westonruter/95da1a34dd4a758e6622c6319c54a60b
 */

// Allow shortcodes to run in Custom HTML widgets.
add_filter( 'widget_custom_html_content', 'do_shortcode' );

/*
 * USAGE:
 *
 * Show content if it is an AMP page:
 * [is_amp_endpoint value=true]<amp-ad>...</amp-ad>[/is_amp_endpoint]
 * or
 * [is_amp_endpoint true]<amp-ad>...</amp-ad>[/is_amp_endpoint]
 *
 * And show content if it is *not* an AMP page:
 * [is_amp_endpoint value=false]<iframe class=ad></iframe>[/is_amp_endpoint]
 * or
 * [is_amp_endpoint false]<iframe class=ad></iframe>[/is_amp_endpoint]
 */

add_shortcode(
	'is_amp_endpoint',
	function( $attr, $content ) {
		$value = true;
		if ( isset( $attr['value'] ) ) {
			$value = rest_sanitize_boolean( $attr['value'] );
		} elseif ( isset( $attr[0] ) ) {
			$value = rest_sanitize_boolean( $attr[0] );
		}
		$is_amp_endpoint = ( function_exists( 'is_amp_endpoint' ) && is_amp_endpoint() );
		if ( $is_amp_endpoint === $value ) {
			$content = do_shortcode( $content );
		} else {
			$content = '';
		}
		return $content;
	}
);

Installation instructions: https://gist.github.com/westonruter/6110fbc4bef0c4b8c021a112012f7e9c

Here's an alternative which is better suited for blocks: https://gist.github.com/westonruter/0769f147e021e0ebfcb04a084987483a