If I type short text into a textarea and submit, then in script.php I already have my text in variable $_POST['text']. However if the text is about 70000 character long, it isn't in $_POST['text']. I can see net log from Firebug and my text is in encoded string, which was sent by my browser to the server. But in $_POST array is my text missing.
Problem solved. It was limit for POST variables on server. Thnx for your time and be careful about webhosting config. I've lost several hours by solving this problem