Enqueue child-theme styles in parent theme

functions.php

<?php

/*
 * *********************************************************************************
 * EDIT: see Justin Tadlock's tried and true method 
 * http://justintadlock.com/archives/2014/11/03/loading-parent-styles-for-child-themes
 * *********************************************************************************
 */

// A more advanced child-theme author can write their own version (e.g. to enqueue other stylesheets).
if ( !function_exists('themename_child_scripts') ) {
	function themename_child_scripts() {
		/* check if active theme is child theme */
		if ( is_child_theme() ) {
			/* if child theme, load child theme's style.css, with parent theme stylesheet as dependency */
			wp_enqueue_style( 'themename-child-style', get_stylesheet_uri(), array('themename-style') );
		}
	}
	/* load child theme stylesheet last */
	add_action('wp_enqueue_scripts', 'themename_child_scripts', PHP_INT_MAX);
}