Function to make photo the post's featured image WordPress

Jurre Hanema answers:

Try adding this to your functions.php:


add_filter('query_vars', 'wpq_query_vars');
add_action('wp', 'wpq_wp');


function wpq_query_vars($qv)
{
$qv[] = 'set_featured';

return $qv;
}


function wpq_wp()
{
if(is_attachment() && get_query_var('set_featured'))
{
global $post;

if($post->post_parent)
update_post_meta($post->post_parent, '_thumbnail_id', get_the_ID());
}
}


function wpq_set_featured_link($post_id = 0)
{
if(!$post_id)
$post_id = get_the_ID();

return add_query_arg(array('set_featured' => 'true'), get_permalink($post_id));
}


In your image.php you can add the link as follows:


<a href="<?php echo wpq_set_featured_link(); ?>">Click me!</a>


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