Empty post data when insert % or `in the html form

Hi ,
i really need help with my website built with codeinigter

1/ i have an html form , methode="post" with a textarea 
    
2/ the problem is that, when the text that i put in the textarea contains %  or ` , the post data is empty when i check it in the controller 

var-dump($_POST)   ----> array(0) {  }
and $this->input->post is NULL

3/ in my local computer it doesn't do that error , even i when i copy and paste the text from word 
but it's online the problem , when i put % or ` in the textarea  , post data is always empty


4/ i think that codeinigter does something in background ( security or something else ... ) i really don't know

could you help me on  this problem please ?