Output a body class based on the WP development environment

wp-dev-env-body-class.php

<?php
/**
 * Adds a body class for the environment.
 *
 * @param  array $classes The current array of body classes.
 * @return array          The new array of body classes.
 */
function hd_env_body_class( $classes ) {

	// if WP environment function exists.
	if ( function_exists( 'wp_get_environment_type' ) ) {

		// add the environment to the body class.
		$classes[] = 'env--' . wp_get_environment_type();

	}

	return $classes;

}

add_filter( 'body_class', 'hd_env_body_class', 10, 1 );