Get hindi text in datatable from database

Question

I have a database which contain hindi text. As I fetched data but getting "???" in place of hindi text.

Here is my code.

<table width="100%" class="table table-striped table-bordered table-hover" id="example">
    <thead>
        <tr>
            <th>Id</th>
            <th>words</th>
            <th>Meaning</th>
        </tr>
    </thead>
    <tbody>
    </tbody>

- database code

$table = 'word_list';

$primaryKey = 'ID';

$columns = array(
    array( 'db' => 'ID', 'dt' => 0 ),
    array( 'db' => 'ID',   'dt' => 1 ),
    array( 'db' => 'Words',     'dt' => 2 )
);

require( 'ssp.class.php' );

echo json_encode(
    SSP::simple( $_GET, $sql_details, $table, $primaryKey, $columns )
);
?>

How could I fetch hindi text properly from database.