Large textinput makes http post fail

I have a form in my application where technicians input information about different events or actions taken (like updating a server). The problem is that these inputs can be quite lengthy and then my form stops working. The server returns a 302 error to the browser if the browsers tries to send data, but just as often the browser does nothing when I try to submit. When the browser does nothing a quick look in the Chrome Developer Tools shows that the browser tries to execute a post to the correct path, but the status is listed as failed. This always occurs if the textarea contains more than ~3500 characters. I've tried to change the enctype to see what happens but it hasn't solved the problem.

<form enctype="application/x-www-form-urlencoded" action="/som开发者_Go百科e/path/" method="post" _lpchecked="1">
<fieldset>
    <input type="hidden" name="machineId" value="some_integer">
    <input type="hidden" name="eventId" value="some_integer">
    Titel:
    <select name="form[title]">
        <option>Some_option</option>
        <option>some_option</option>
    </select>

    <textarea name="form[text]" rows="25" cols="90"></textarea>
    <input type="submit" value="Spara" title="Spara">
</fieldset>
</form>

Any ideas on why it doesn't work and what can be done?

EDIT: My application is based on PHP and running on Debian/Apache. I haven't been able to find any settings that might prevent the post from working correctly. I do have a post_max_size set at 8MB, but a text of 3500 chars are not larger than 8MB so...

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Your text via POST will most likely NOT be 1 byte/character. Apache mod_security might be filtering the data. And it could be any other number of Apache mods that affect post encryption. You might check out mb_get_info() and other mb_* functions to verify how PHP is encoding the text. If you don't want to have to dig too deeply, you can make an educated guess from a couple data points as to how many bytes per character are being used in your POST and adjust post_max_size to suit your needs.

If you are cannot print errors to screen, you can check out

tail -n 30 /var/log/apache2/error.log #prints last 30 lines of error.log

immediately after your white screen symptom to get more detailed information on errors/warnings/etc encountered during the script.

Also note that post_max_size is limited by memory_limit ... I don't think that is the issue, but it may be something to consider for another reader.

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what server side language you are using? maybe you need some text compression like this one Huffman Algorithm