How do I preload .css and .js files, before the whole page (dynamic by PHP) is generated

How do I preload .css and .js files, before the whole page (dynamic by
PHP) is generated

My homepage (index.php) is generated dynamicly by PHP, so it takes about
1s till the the page is delivered to the user.
Because my css and js script is in the header of (index.php), after this
1s the css and js will start to download.
Is there some general way of preloading this js and css files?



My aproach would be to delete all content of index.php, include just
<'head> with my css and js file, and then do some js to load the whole
indexOriginal.php (with the dynamic content generated on my server by
PHP), so this should enable the user to download the css, js in parallel
of indexOriginal.php.
Is this the right aproach?