ph

ph assigns an explicit name to a message placeholder. It is useful when an interpolation is a property access, function call, or other complex expression that would otherwise receive a numeric placeholder such as {0}.

The key gives translators a meaningful placeholder name, while the value remains the expression evaluated at runtime.

For the framework-agnostic Lingui semantics, see the official ph reference.

Source

Demo.svelteCatalog

<p>{$t`Hello ${ph({ username: user.profile.displayName })}`}</p>
<p><Trans>Welcome {ph({ username: user.profile.displayName })}!</Trans></p>

#: src/demos/macros/ph/Demo.svelte
msgid "Hello {username}"
msgstr "Hello {username}"

#: src/demos/macros/ph/Demo.svelte
msgid "Welcome {username}!"
msgstr "Welcome {username}!"

Result

PreviewTransformed SvelteCompiled Catalog

Hello Lingui

Welcome Lingui!

<p>{$__l4s_translate(
/** i18n */
{
  id: "MsjnH4",
  values: {
    username: user.profile.displayName
  }
})}</p>
<p><L4sRuntimeTrans {.../** i18n */
{
  id: "pNCIOi",
  values: {
    username: user.profile.displayName
  }
}} /></p>

/*eslint-disable*/
import type { Messages } from "@lingui/core";
export const messages = JSON.parse(
  "{\"MsjnH4\":[\"Hello \",[\"username\"]],\"pNCIOi\":[\"Welcome \",[\"username\"],\"!\"]}",
) as Messages;

Locale

ENJA

Name

Usage

Svelte

<script lang="ts">
  import { ph, t, Trans } from "lingui-for-svelte/macro";

  let user = $state({ name: "Ada" });
</script>

<p>{$t`Hello ${ph({ username: user.name })}`}</p>
<Trans>Welcome {ph({ username: user.name })}!</Trans>

Use ph inside reactive $t expressions or component macros. For an intentional non-reactive script snapshot, the same placeholder syntax works inside t.eager.

Astro

---
import { ph, t, Trans } from "lingui-for-astro/macro";

const user = { name: "Ada" };
const greeting = t`Hello ${ph({ username: user.name })}`;
---

<p>{greeting}</p>
<Trans>Welcome {ph({ username: user.name })}!</Trans>

Official Lingui

import { ph, t } from "@lingui/core/macro";

const greeting = t`Hello ${ph({ username: getUser().name })}`;

Extracted message and runtime values

Given this source:

t`Hello ${ph({ username: user.name })}`;

the catalog receives a meaningful ICU placeholder:

Hello {username}

The transform keeps the original expression in the runtime value mapping:

{
  message: "Hello {username}",
  values: {
    username: user.name,
  },
}

Tip

Simple variables already keep their names. Write t`Hello ${name}` unless the expression is complex or a different translator-facing name would make the message clearer.

Syntax rules

• Pass an object with exactly one property to ph.
• The property key becomes the ICU placeholder name.
• The property value is evaluated at runtime and stored under that name in values.
• Keep names stable and descriptive, such as username, startDate, or itemCount.

When ph is a good fit

• a property access or function call would otherwise become {0}
• translators need to understand what a placeholder represents
• a stable placeholder name makes catalog changes and reviews easier to follow