When inserting a string that include html entities, string is cutted off

Question

I have a form that similar to one below.

   <form action="" method="POST">
     <input type="text" name="header" />
     <textarea id="ck_editor" name="content"></textarea>
   </form>

When form sent I replace special characters like Ğ, Ş, Ü with their corresponding html entity. Then insert edited string to database with PHP/MySQLI. content is inserted without any problem. But when it comes to header, it is cutted of after special character's position.

When I want to insert

Türkçe Karakter

It inserted to table like

T

I echo out header, content variables - without any problem - to notify whether inserting proccess is successel or not. MySQL Table

icerik_id INT(11) AUTO_INCREMENT PRIMARY
icerik_baslik VARCHAR(255) 
icerik_icerik TEXT
icerik_durum INT(11) DEFAULT = '1'
collation utf8_unicode_ci

How can I solve this problem?

PHP Code // (icerik = content) (baslik = header)

 if ($_POST) {

    ... 

    if ($ekle == true) {
            // Girdileri Düzenle
            // HTML Entity
            $baslik = htmlentities($baslik, ENT_COMPAT, "UTF-8");
            $icerik= htmlentities($icerik, ENT_COMPAT, "UTF-8");


            $ekle_db = $db->query("INSERT INTO icerikler SET
                icerik_baslik = '$baslik',
                icerik_icerik = '$icerik'
            ");

            if ($ekle_db) {
                $ekle_msg[] = "<span style='color: rgba(140,200,30,1)'>İçerik Başarıyla Eklendi:</span> $baslik";
                $ekle = true;
            } else {
                $ekle_msg[] = "<span style='color: red'>İçerik Eklenenemdi.</span>";
                $ekle = false;
            }
        }

        ...
     }