<select class="form-control" name="kategori_secim">
<option hidden value=""> <?=$sonuc['kategori_secim'];?> </option>
<?php
$alt = $dbh->query("select * from category ", PDO::FETCH_ASSOC);
if ($alt->rowCount()) {
foreach ($alt as $alt) {
echo '<option '.($alt['id']==$sonuc["kategori_secim"]?"selected":"").' value="' . $alt['id'] . '">' . $alt['baslik'] . '</option>';
echo '</optgroup>';
}
}
?>
 </select>