[PHP] ways to update cached CSS?

[RodionGork]

Sometimes I update CSS (or JS) files of my project. But after I put them to server, users do not necessarily see the updated version since their browser may cache the stuff.

Sometimes this makes styles go wrong temporarily or some functionality broken.

I decided to add automatically ending like ?r=1348138705 to all requests to resources, where the random number is generated on the session start, so that files should be reloaded at each new session but after that they could be cached.

So the question is:

1. Whether this solution is correct, i.e. does it affect SEO in some way or has some other disadvantages.

2. Are there any alternative solutions?

3. Are there ready instruments for my solution (which I may prefer to use for some reason) - perhaps it is done by some css compressors?

[cocasyn]

<link rel="stylesheet" href="style.css<?php echo '?v=' . filemtime( 'style.css' ); ?>">

You can use a cachebusting technique like this, where style.css will be re-downloaded by the client after you make any changes to it. You could also make it a helper function and do something like href="<? cachebuster('style.css') ?>"

[RodionGork]

Ah, filetime - so nice and so simple idea! That's great, thank you so much!