saya kurang tahu apa ini bisa?

<?php
error_reporting(E_ALL);
$tampil=mysql_query("SELECT * FROM tb_kategori ORDER BY id_kategori ASC")or die('error:salah query kategori');
$no=1;
$sql="SELECT count(id_kategori) c FROM tb_hasil_temp WHERE username='{$_SESSION['username']}' AND id_kategori='%s";
//$cek=mysql_query($sql);
//$c=mysql_fetch_array($cek);
while ($r=mysql_fetch_array($tampil)){
echo"<tbody><tr>
<td>$r[id_kategori]</td>
<td>$r[nama_kategori]</td>";
    $sqlCari=sprintf($sql, $r['id_kategori']);
    $cek=mysql_query($sql) or die('error:'.$sql);
    $c=mysql_fetch_array($cek);
    if (empty($c['c']==0)){
        echo"<td><input type='button' value='Kategori $no' onClick='openWin$no()'></td>";
    }
    else{
        echo"<td> Sudah Mengerjakan</td>";
    }

    echo"</tr>
    </tbody>";
    $no++;
}