Add Course Name in Lesson's body classes LifterLMS

course-name-in-lesson-body-class.php

<?php  // Do not copy this line

// Copy from under this line and paste into your child theme's functions.php

function llms_course_name_in_body_class( $classes ) {
	
	// bail early, if we're not on a lesson.
	if( ! is_singular ( 'lesson' ) ){
		return $classes;
	}
	
	global $post;
	$lesson = new LLMS_Lesson( $post->ID );
	
	// get the course slug.
	$course_name = basename( get_permalink( $lesson->get_parent_course() ) );
	
	// add course-{course-slug} as a class to the body.
	return array_merge( $classes, array( "course-$course_name" ) );
}

add_filter( 'body_class', 'llms_course_name_in_body_class' );