$varmi = $db->prepare("SELECT COUNT(*) as count FROM uyeler WHERE uye_mail=:uye_mail");
$varmi->execute([':uye_mail' => $uye_mail]);
$row = $varmi->fetch(PDO::FETCH_ASSOC);
$emailCount = $row['count'];

if($emailCount > 0){
    echo "emailvar";
} else {
    echo "emailyok: " . $uye_mail;
}