By default Rich Text Editor maps most special characters to the equivalent HTML entity automatically. You can turn it off by setting this property to "false".
Example
<?php
$rte=new RichTextEditor();
$rte->Text="Type here";
$rte->UseHTMLEntities=false;
$rte->ID="Editor1";
$rte->MvcInit();
echo $rte->GetString();
// use $_POST["Editor1"]to retrieve the data
?>