I have my web portfolio.
On my main page I have recently 6 added works from database(works with descriptions).
I have created a php script ,php script generaeted keywords from 6 texts more then 100 keywords.When page loaded ,sript randomly generate 10 keywords from 100
My recommendation would be not to do this. From a users perspective (and always try to keep that in mind when working on your SEO), why would your page be about 10 topics the one moment and about 10 different topics just moments later. And again and again... Even more so as this seems rather unstable and inconsistent to the Search Engines!
Make sure you have pages that are about a certain subject within your website. Choose your keywords wisely and update these in you meta tags. When you page outgrows the subject you can create a new page for the additional subject. And so on. It gives a proper hierarchy and steady growth of your website.
Please note that you will only be doing this for search engines other than Google, as Google is fully neglecting the keyword meta tags: http://googlewebmastercentral.blogspot.com/2009/09/google-does-not-use-keywords-meta-tag.html
My expectation is that it won't be long before Bing, Yahoo, etc etc will do the same. So my advice will be not to waste your energy on keyword meta tags. I do not use these at any of my sites. There has been no effect on my SERP results or website visitors whatsoever since I have made this change. And it saved me a LOT of time ;)