[WordPress] Override the default post title with a custom field.

wp-override-title.php

// Only override the title on the front-end.
if ( ! is_admin() && ( ! defined( 'DOING_AJAX' ) || ! DOING_AJAX ) ) {
	add_filter( 'the_title', 'PREFIX_override_post_title', 10, 2 );
}
/**
 * Override the_title() with a custom field if it is specified.
 *
 * @param   string  $title  Original post title.
 * 
 * @return  string  $title  Update post title.
 */
function PREFIX_override_post_title( $title, $id ) {

	$custom_title = get_post_meta( $id, 'custom_title', true );
			

	if ( ! empty( $custom_title ) ) {
		$title = $custom_title;
	}

	return $title;
}