Impossible d enregistrer texte area dans sql

<script src="//tinymce.cachefly.net/4.2/tinymce.min.js"></script>
<?php include '_database/database.php' ?>
<?php          
    $sql = "SELECT * FROM rules";
    $result = mysqli_query($database,$sql) or die(mysqli_error($database)); 
    $rules = mysqli_fetch_array($result);
?>         
    <!-- Tab panes -->
    <div class="tab-content">
        <div class="tab-pane fade in active" id="general">         
            <div class="col-md-12">

                <form action="components/update-rules.php" method="post" enctype="multipart/form-data" id="UploadForm">                    
                    <input type="hidden"  name="rules_id" value="<?php echo $rules['rules_id'];?>"/>
    			   <input type="hidden" name="user_username" value="<?php echo $current_user;?>"/>
                    <textarea id="post_body" class="form-control" name="rule_txt" value="" style="height:300px;"><?php echo $rules['rule_txt'];?></textarea>

               
    
      	  </div>
        </div>
    </div>
<br>
    <div class="submit">
        <center>
            <button class="btn btn-primary ladda-button" data-style="zoom-in" type="submit"  id="SubmitButton" value="Upload" />Edit rules</button>
        </center>
    </div>
</form>

 <?php
      ini_set("display_errors",1);
    session_start();
    if(isset($_POST)){
        require '../_database/database.php';
        $user_username=$_REQUEST['user_username'];
		$rule =htmlspecialchars($_REQUEST['rule_txt']);
		$rule_txt = addslashes($rule);
        $sql3="UPDATE rules SET user_username='$user_username',rule_txt='$rule_txt' WHERE rules_id=1";
            mysqli_query($database,$sql3)or die(mysqli_error($database));
            header("location:../edit-rules.php?status=success");
    }    
?>