Global-less WordPress Templating

functions.php

<?php

/**
 * WordPress template renderer that avoids using global variables
 * @param string Name of a template to load
 * @param array $args Template variables
 * @return string|WP_Error rendered template or an error
 * NOTE: Untested
 */
function render_template( $template_name, array $args ) {
	
	$file = locate_template( [$template_name], false);
	
	if( '' === $file || !file_exists( $file ) ) {
		return new WP_Error( 'not found', __( 'The requested template file could not be found', 'textdomain' ), $template_name );
	}
		
	ob_start();
	include $filename;
	return ob_get_clean();
}