Post data that contains paths with ../../ gives empty $_POST array - php

Question

Recently I moved my codeigniter website to a new server (goddady). Before this everything was working great with no problems. But now I started to get strange problems with post data, whenever I try to insert data that contains relative paths with dots (../../) and try to submit the form, I get an empty $_POST array. The strange thing is that this happens only with certain forms, not all of them. What could cause such problem?
Here is the form that causes problem:
<?php
if(isset($posts2) && count($posts2) == 1){
$posts2 = $posts2[0];
echo form_open_multipart('professors/update_biography/', array("id" => "professors_edit"));
echo form_hidden('posts2[id]', $posts2->id);
if(isset($user) && count($user) == 1){
$user = $user[0];
echo form_hidden('user[id]', $user->id);
echo form_hidden('user[role]', "Professor");
}
?>
<table class="admin_table">
<tr>
<th>
Биографија
</th>
<td>
<textarea name='posts2[biography]'><?php echo $posts2->biography; ?></textarea>
</td>
</tr>
<tr>
<th>
Биографија EN
</th>
<td>
<textarea name='posts2[biography_en]'><?php echo $posts2->biography_en; ?></textarea>
</td>
</tr>
<tr>
<th>
Cv
</th>
<td>
<p class="old">CV</p>
<input type="file" name='cv' id="pdf"></input>
</td>
</tr>
<tr>
<td> </td>
<td>
<input type='submit' name='submit' value='Зачувај' />
</td>
</tr>
</table>
<?php
echo form_close();
?>
<div class="redButton" style="float:left; width: 150px;">
<?php
if(!isset($prof[0]->id)){ //da ne go prikazuva za profesor
echo anchor('professors/', 'Назад до професори');
}
?>
</div>
<?php
}
?>