Description:
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Sometimes if form is submitted, I get strange data on the server in php. It happens only about 3 times a day mostly using IE.
It seems that the problem might be in the encoding on the client, even though I set the corrent charset using "header('Content-Type: text/html; charset=UTF-8');" as soon as possible.
Sometimes I get some HTML tags in the field data e.g. (<table cellpadding= or <input type=)


Reproduce code:
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form definition
<form action="..." method="post" class="search-form" name="reservation_form" id="reservation_form">

There are 2 buttons for submition:

<input type="submit" value="Book" class="submit_button" style="width:165px" />

<button type="submit" name="info_only" style="width:165px" value="1" class="submit_button with_value">Inform</button>



Expected result:
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Correct form fields data.
objekt 15010 pouze v p??pad? ceny 838 CZK za pokoj a noc se sn?dan?

Actual result:
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objekt 15010 pouze v p%u0159&#56353;d%u011B ceny 838 CZK za pokoj a noc se sn&#55585;n&#55456;/>

										<table cellpadding=