php - Question mark( �) displaying instead of each Bengali unicode character. How to fix it?

The problem is confusing,such as,

When I am trying to display a Bengali unicode word,'কলম' with this

 $data=$_POST['data'];
 echo $data;

Then it displays the word 'কলম' properly as I wanted,

But when I split the word character by character with this

    for($i=0;$i<3;$i++)
    {
        echo $data[$i];         
        echo "+";
    }

Then it display '�+�+�+' instead of displaying like this 'ক+ল+ম+'.

How to solve this problem .Thank you.

For information , I have declared charset utf-8 in head.

< meta http-equiv= " Content-Type " content= " text/html;
charset=utf-8 " />

Answer

Use mb_substr($data, $i, 1) instead. You are using a multi-byte string.