When sending a form via ajax the textarea get cutted off

I have a form where i send a input type = text and a textarea. Sending the data through ajax to a php file in a external url.

var postdata = $("#form_write_comment").serialize();

$.post( url , postdata, function( data ) {
    data = $.parseJSON(data);
    if(data.error!=true){
        console.log(data);          
    }else{
        $('.errormsg').html(data.errormsg); 
    }
});

In the php file I get everything right, but the textarea value reaches cut .

I already tried to escape () to the value of the text area, but do not work .

Thaks, sorry for my bad english.