Once Props

A once prop is resolved once and remembered by the client, which sends its key back in X-Inertia-Except-Once-Props. While the client has it, the server skips it — the Closure is not even called — and the client reuses its copy:

return $this->inertia->render($request, $response, 'Billing/Plans', [
    'plans' => Inertia::once(fn() => $this->plans->all()),
]);

{
    "props": {"errors": {}, "plans": [...]},
    "onceProps": {"plans": {"prop": "plans", "expiresAt": null}}
}

The client forgets a once prop on a page without it. A partial reload that asks for it always gets it, and a first visit always sends every once prop.

Expiry

until() sets when the client forgets the prop: in seconds, as an interval or as a time.

'rates' => Inertia::once(fn() => $this->rates->today())->until(3600),
'rates' => Inertia::once(fn() => $this->rates->today())->until(new DateInterval('P1D')),
'rates' => Inertia::once(fn() => $this->rates->today())->until(new DateTimeImmutable('tomorrow')),

The expiry is computed when until() is called, so build once props per request.

Refreshing

fresh() sends the prop although the client has it, for when the data behind it has changed:

'plans' => Inertia::once(fn() => $this->plans->all())->fresh($this->plans->changedSince($since)),

Keys

A once prop is remembered under its path. as() names the key, so pages that call the prop differently share it:

// Team/Index
'memberRoles' => Inertia::once(fn() => $this->roles->all())->as('roles'),

// Team/Invite
'availableRoles' => Inertia::once(fn() => $this->roles->all())->as('roles'),

A backed enum works as a key too.

Combined

once() turns any prop but an always prop into a once prop, and as(), until() and fresh() do too:

'permissions' => Inertia::defer(fn() => $this->permissions->all())->once(),
'activity' => Inertia::merge(fn() => $this->activity->recent($user))->once(),
'categories' => Inertia::optional(fn() => $this->categories->all())->until(600),

Shared once props are the usual case: see shared data.