Get Wordpress Featured Image "alt"

Question

I'm trying to get a page's featured image alt and echo it as paragraph text but my code doesn't seem to be working.

I'm currently able to echo the image and it's working perfectly.

Here's the code I'm using:

    <?php
    get_header(); ?>
      </div>
    <?php /* The loop */ ?>
    <?php while ( have_posts() ) : the_post(); ?>
    <div class="header-image">

    <?php echo get_the_post_thumbnail($page->ID, 'full'); ?> 
    
    <?php $alt = get_post_meta( $attachment_img->ID, '_wp_attachment_image_alt', true ); ?>
    
    <p><?php echo $alt; ?></p>
    
    </div>

Answer 1

Check if you get correct thumbnail id.
For me this code works perfect:

$thumbnail_id = get_post_thumbnail_id( $post->ID );
$alt = get_post_meta($thumbnail_id, '_wp_attachment_image_alt', true);