modify .htaccess using CODEIGNITER

I have a section where I want to edit the .htaccess file using a <textarea> field ... but here comes the problem, this is my original htaccess:

<IfModule mod_rewrite.c>
RewriteEngine On

RewriteCond $1 !^(index\.php|resources|robots\.txt)
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php/$1 [L,QSA]

order deny,allow
deny from all

allow from 187.192.43.11     # Oficina NUEVA
allow from 187.192.43.39     # Oficina NUEVA



</IfModule>

ErrorDocument 401 /admin/errors/error.php 
ErrorDocument 403 /admin/errors/error.php
ErrorDocument 404 /admin/errors/error.php 
ErrorDocument 500 /admin/errors/error.php 

And when I save it, I keep it in the database like this:

<IfModule>
RewriteEngine On

RewriteCond $1 !^(index\.php|resources|robots\.txt)
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php/$1 [L,QSA]

order deny,allow
deny from all

allow from 187.192.43.11     # Oficina NUEVA
allow from 187.192.43.39     # Oficina NUEVA



</IfModule>

ErrorDocument 401 /admin/errors/error.php 
ErrorDocument 403 /admin/errors/error.php
ErrorDocument 404 /admin/errors/error.php 
ErrorDocument 500 /admin/errors/error.php 

I do not know why you save this <IfModule> instead of this <IfModule mod_rewrite.c>

My view:

<form id="form" name="form" action="<?=base_url()?>controlip/guardarhtaccess" method="POST">
<!---->
<input type="hidden" name="idhtaccess"  value="">
<!---->
<input type="hidden" name="fechamodificacionhtaccess"  value="<?php echo date('d-m-Y');?>">
<!---->
<textarea style="height: 500px;" class="input_edit_client" name="contenidohtaccess" id="contenidohtaccess">
<?php
$archivo = file_get_contents("../admin/.htaccess");
$archivo = ucfirst($archivo);
echo $archivo;
?>
</textarea>
<!---->
<br>
<!---->
<input class="btn_save_edit" type="submit" name="guardar" id="guardar" value="GUARDAR" style="margin-bottom: -15px;background: #252525;margin-top: 10px;font-size: 14px;padding: 5px 15px;">
<!---->
</form>

My controller:

function guardarhtaccess(){

        $contenidohtaccess=$this->input->post('contenidohtaccess',TRUE);

        $fichero = "/homessd/wwwhr1/public_html/admin/prueba.txt";

        file_put_contents($fichero, $contenidohtaccess);

        $data= array(
        'idhtaccess' =>0,
        'fechamodificacionhtaccess' => time(),
        'contenidohtaccess' =>$this->input->post('contenidohtaccess',TRUE),
        );

        $this-> realhtaccess -> savehtaccess($data);

        redirect('controlip');

        }

My model:

function savehtaccess($data)
 {   
  if($data[$this->ID]==0)
  {
    if($this->db->insert($this->Table, $data))
     {
        return true;
     }
    else 
       return false;
  }
  else
  {
    $this -> db -> where($this->ID, $data[$this->ID]);    
    $this -> db -> update($this->Table,$data);
  }
}

and then the problem I have is that I delete this "mod_rewrite.c" from this tag <IfModule>