my_enqueue_inline_style.php

function my_enqueue_inline_style ( $handle, $src = '', $deps = array(), $ver = false, $media = 'all' ) {
	if ( $src ) {
		wp_enqueue_style( $handle, $src, $deps, false, $media ); 
	}
	add_filter( 'style_loader_tag', function ( $html, $this_handle, $href, $media ) use ($handle)  {
		if ($this_handle !== $handle) {
			return $html;
		}
		$css_url = explode('?', $href)[0];
		$css_path = str_replace(site_url(), ABSPATH, $css_url);
		$base_dir = dirname($css_path) . '/';

		$css = file_get_contents( $css_path );

		// convert relative url to absolute
		$css = preg_replace_callback("/url\((?![\'\"]?[http:|data:|\/])[\'\"]?(.+?)[\'\"]?\)/s", function ($matches) use ($base_dir) {
			$relative = $matches[1];
			while ( strpos($relative, '../') === 0 ) {
				$relative = substr($relative, 3);
				$base_dir = preg_replace('/[^\/]+?\/$/', '', $base_dir);
			}
			if ( strpos($relative, './') === 0 ) {
				$relative = substr($relative, 2);
			}
			$path = $base_dir . $relative;
			$url = str_replace(ABSPATH, site_url(), $path);
			return "url('$url')";
		}, $css);

		// Minify
		$css = preg_replace('/\/\*((?!\*\/).)*\*\//', '', $css); 
		$css = preg_replace('/\s{2,}/', ' ', $css);
		$css = preg_replace('/\s*([:;{}])\s*/', '$1', $css);
		$css = preg_replace('/;}/', '}', $css);

		return "<style media='$media'>/* $url */\n$css\n</style>\n";
	}, 10, 4 );

}