Using WordPress ‘customize_partial_render’ PHP filter

The customize_partial_render WordPress PHP filter allows you to modify the rendering of a partial value in the Customizer.

Usage

add_filter( 'customize_partial_render', 'your_custom_function', 10, 3 );

function your_custom_function( $rendered, $partial, $container_context ) {
    // Your custom code here

    return $rendered;
}

Parameters

$rendered (string|array|false): The partial value. Default false.
$partial (WP_Customize_Partial): WP_Customize_Setting instance.
$container_context (array): Array of context data associated with the target container.

More information

See WordPress Developer Resources: customize_partial_render

Examples

Change site title

Modify the site title in the Customizer.

add_filter( 'customize_partial_render', 'change_site_title', 10, 3 );

function change_site_title( $rendered, $partial, $container_context ) {
    if ( 'blogname' === $partial->id ) {
        $rendered = '<h1 class="site-title">' . get_bloginfo( 'name' ) . '</h1>';
    }
    return $rendered;
}

Add custom text to site description

Add custom text to the site description in the Customizer.

add_filter( 'customize_partial_render', 'add_custom_text_to_description', 10, 3 );

function add_custom_text_to_description( $rendered, $partial, $container_context ) {
    if ( 'blogdescription' === $partial->id ) {
        $rendered .= ' - Custom Text';
    }
    return $rendered;
}

Modify the navigation menu in the Customizer.

add_filter( 'customize_partial_render', 'modify_navigation_menu', 10, 3 );

function modify_navigation_menu( $rendered, $partial, $container_context ) {
    if ( 'nav_menu' === $partial->type ) {
        $rendered = str_replace( 'menu-item', 'custom-menu-item', $rendered );
    }
    return $rendered;
}

Add a custom CSS class to a widget in the Customizer.

add_filter( 'customize_partial_render', 'add_custom_css_class_to_widget', 10, 3 );

function add_custom_css_class_to_widget( $rendered, $partial, $container_context ) {
    if ( 'widget' === $partial->type ) {
        $rendered = str_replace( 'class="widget', 'class="custom-widget', $rendered );
    }
    return $rendered;
}

Modify footer text

Modify the footer text in the Customizer.

add_filter( 'customize_partial_render', 'modify_footer_text', 10, 3 );

function modify_footer_text( $rendered, $partial, $container_context ) {
    if ( 'footer_text' === $partial->id ) {
        $rendered = str_replace( 'Powered by WordPress', 'Custom Footer Text', $rendered );
    }
    return $rendered;
}