Howto keep header image when changing theme

Question

We have a setup where bloggers can and will have their theme changed. Is it possible to migrate the existing header image to the new theme ? I know how to override the header image with the add_filter, also know how to get the current header image. The issue here is to keep the header image when changing the theme. Is that possible ?

Answer 1

Here comes the plugins to rescue, move that code into a plugin and activate. That'll not change header image upon every theme change.

E.g -

<?php
/*
Plugin Name: keep header always
*/

// Your code to keep header image

?>

save it as whatever-foo.php upload to /wp-content/plugins/ directory and activate it

Answer 2

The header image is set per …

set_theme_mod( 'header_image', $choice['url'] )

… a wrapper for …

update_option( 'theme_mods_' . get_option( 'stylesheet' ), $value );

So you can hook into …

'pre_update_option_theme_mods_' . get_option( 'stylesheet' )

… take the first parameter, which is an array of all theme mods, and save the value of the key 'header_image' in a plugin option. The key 'header_image_data' stores the meta data for that image.

Then filter 'theme_mod_header_image' to return your stored plugin option if there is no image set.

Answer 3

We did a small mu-plugin that solved our issue.

Here is the code

add_action('pre_update_option_stylesheet', 'phi_pre_update_option_stylesheet');
add_action('switch_theme', 'phi_switch_theme');

function phi_pre_update_option_stylesheet($stylesheet)
{
    update_option('previous_header_image_saved', get_theme_mod('header_image'));

    return $stylesheet;
}

function phi_switch_theme()
{
        if (get_option('previous_header_image_saved')) {
                set_theme_mod('header_image', get_option('previous_header_image_saved'));
            delete_option('previous_header_image_saved');
    }
}