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# 6.4 Validasi Form Sederhana

Validasi membantu memastikan data yang masuk sesuai aturan.

Anda akan memeriksa field wajib, panjang input, dan format sederhana seperti email.

### Tujuan belajar

Setelah mempelajari bagian ini, Anda diharapkan bisa:

* memahami fungsi validasi
* memeriksa input wajib
* membuat aturan sederhana untuk data pengguna

### Apa itu validasi

Validasi adalah proses memeriksa apakah data sudah sesuai kebutuhan program.

Misalnya:

* nama tidak boleh kosong
* password tidak boleh terlalu pendek
* email harus berformat wajar

### Validasi input kosong

```php
<?php
$nama = trim($_POST["nama"]);

if ($nama == "") {
    echo "Nama wajib diisi";
}
?>
```

### Validasi panjang karakter

```php
<?php
$password = trim($_POST["password"]);

if (strlen($password) < 6) {
    echo "Password minimal 6 karakter";
}
?>
```

### Validasi format email

```php
<?php
$email = trim($_POST["email"]);

if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
    echo "Format email tidak valid";
}
?>
```

### Contoh gabungan sederhana

```php
<?php
$nama = trim($_POST["nama"]);
$email = trim($_POST["email"]);

if ($nama == "") {
    echo "Nama wajib diisi";
} elseif (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
    echo "Email tidak valid";
} else {
    echo "Data valid";
}
?>
```

### Kenapa validasi penting

Tanpa validasi, program bisa menerima data yang salah.

Akibatnya, hasil program bisa kacau atau data yang disimpan menjadi tidak rapi.

### Kesalahan umum

* hanya membersihkan data tetapi tidak memeriksanya
* validasi terlalu sedikit
* pesan error tidak jelas

### Latihan singkat

Buat validasi untuk:

* nama tidak boleh kosong
* email harus valid
* password minimal 6 karakter

### Poin evaluasi bab 6.4.

Pastikan Anda sudah memahami poin berikut:

* Saya paham fungsi validasi dalam form.
* Saya bisa memeriksa input kosong.
* Saya bisa memeriksa panjang data dan format email.
* Saya tahu kapan data dianggap valid.

Jika semua sudah jelas, lanjut ke [Praktik: Form Registrasi Siswa Baru](/php/bab-6-penanganan-form/praktik-form-registrasi-siswa-baru.md).


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