select data from database using checkboxes in php from mysql

I am working on customise report of a user.In this page I give a option of user check boxes for select data from database.Means user select the data which he wants to see from table.My table have many fields like name , block,contact..and so more. If users wants to see only uid and name only then he check the boxes of name and phone only. my checkboxes are

       <form action="#" method="post">
 <input type="checkbox" name="check_list[]" value="uid"><label>uid</label>
<input type="checkbox" name="check_list[]" value="name"><label>name</label>
<input type="checkbox" name="check_list[]" value="block"><label>block</label>....and so more
 <input type="submit" name="submit" value="Submit"/>
</form>

and php code I am trying is

    if(isset($_POST['submit'])){

    $sql[] = "select ";

    foreach($_POST['check_list'] as $selected){
        $sql[]=$selected.',';
    }  

    $sql[]= " from emitra_basic LIMIT 5";

    foreach ($sql as $user) {

        $ram="$user";
    }

    if ($result=mysqli_query($conn, $ram))
    { 
        while ($row=mysqli_fetch_row($result))
        { 
            echo "id".$row['uid']."<br/>";
            echo "name".$row['name']."<br/>";
        }
    }
}  

But No result.what should i try?