Transform Eloquent Attributes with withCasts()

Sometimes a query returns a calculated value that you want Laravel to treat as a specific data type.

For example, you might retrieve a date through a subquery but want to access it as a Carbon date instead of a plain string.

Rather than adding a permanent cast to your model, Laravel provides withCasts().

Basic Usage

Imagine your User model has a subquery that retrieves the latest login time:

$users = User::query()
    ->select('users.*')
    ->selectSub(
        Login::select('created_at')
            ->whereColumn('user_id', 'users.id')
            ->latest()
            ->limit(1),
        'last_login_at'
    )
    ->withCasts([
        'last_login_at' => 'datetime',
    ])
    ->get();

Now Laravel casts last_login_at to a date-time value for these query results.

Access the Casted Value

foreach ($users as $user) {
    if ($user->last_login_at) {
        echo $user->last_login_at->format('d M Y H:i');
    }
}

Because the attribute is cast to datetime, you can use Carbon's date-formatting methods.

Why Not Add It to $casts?

You could define the cast permanently on the model:

protected function casts(): array
{
    return [
        'last_login_at' => 'datetime',
    ];
}

But if last_login_at exists only in a particular query, a permanent cast may be unnecessary.

withCasts() keeps that behavior close to the query that needs it.

When Should You Use It?

• Casting subquery results
• Formatting calculated date attributes
• Handling query-specific numeric values
• Applying temporary casts to selected columns