Polylang Object Translations

Polylang Object Translations

Use this skill when code needs to read or write the relationship between translated posts or translated terms.

Polylang stores language and translation relationships through private taxonomies, not custom tables:

Do not write those terms or term descriptions directly. Use Polylang APIs so caches, cleanup, validation, and synchronization hooks run.

Resolve translated IDs

For posts:

$translated_id = pll_get_post( $post_id, 'fr' );

if ( $translated_id > 0 ) {
    $post = get_post( $translated_id );
}

For terms:

$translated_term_id = pll_get_term( $term_id, 'fr' );

Important return behavior in Polylang 3.8.5:

• pll_get_post() returns an integer ID.
• pll_get_term() returns an integer ID.
• Missing translation, invalid language, or object without language returns 0, not false.
• If the requested language is the object's own language, the original ID is returned.

When $lang is omitted, both functions use pll_current_language(). In cron, CLI, imports, and many admin tasks, pass the language explicitly.

Read language and groups

$post_lang = pll_get_post_language( $post_id );          // slug or false.
$term_lang = pll_get_term_language( $term_id, 'locale' );
$lang_obj  = pll_get_post_language( $post_id, \OBJECT );

$post_translations = pll_get_post_translations( $post_id );
$term_translations = pll_get_term_translations( $term_id );

Translation arrays are keyed by language slug and contain object IDs:

array(
    'en' => 123,
    'fr' => 456,
)

Only trust arrays returned by Polylang. The model validates languages and object IDs before saving.

Create posts with language

Polylang 3.7+ provides pll_insert_post() and pll_update_post() wrappers:

$post_id = pll_insert_post(
    array(
        'post_type'   => 'book',
        'post_status' => 'publish',
        'post_title'  => 'Hello',
    ),
    'en'
);

if ( is_wp_error( $post_id ) ) {
    return $post_id;
}

Create a translation and link it in one pass:

$fr_id = pll_insert_post(
    array(
        'post_type'    => 'book',
        'post_status'  => 'publish',
        'post_title'   => 'Bonjour',
        'translations' => array(
            'en' => $post_id,
        ),
    ),
    'fr'
);

Update language or group on an existing post:

$result = pll_update_post( array(
    'ID'           => $fr_id,
    'lang'         => 'fr',
    'translations' => array(
        'en' => $post_id,
        'fr' => $fr_id,
    ),
) );

pll_insert_post() returns WP_Error( 'invalid_language' ) for an invalid language. Do not call wp_insert_post() and patch Polylang's private taxonomies by hand.

Create terms with language

Use the term wrappers:

$term = pll_insert_term(
    'News',
    'category',
    'en',
    array(
        'slug' => 'news',
    )
);

if ( is_wp_error( $term ) ) {
    return $term;
}

Create and link a translated term:

$fr_term = pll_insert_term(
    'Actualites',
    'category',
    'fr',
    array(
        'slug'         => 'actualites',
        'translations' => array(
            'en' => (int) $term['term_id'],
        ),
    )
);

Update:

pll_update_term( (int) $fr_term['term_id'], array(
    'lang'         => 'fr',
    'translations' => array(
        'en' => (int) $term['term_id'],
        'fr' => (int) $fr_term['term_id'],
    ),
) );

Term parents are language-sensitive. When creating hierarchical translated terms, translate the parent ID first.

Link existing objects

When objects already exist, set language before saving translations:

pll_set_post_language( $en_id, 'en' );
pll_set_post_language( $fr_id, 'fr' );

$saved = pll_save_post_translations( array(
    'en' => $en_id,
    'fr' => $fr_id,
) );

For terms:

pll_set_term_language( $en_term_id, 'en' );
pll_set_term_language( $fr_term_id, 'fr' );

$saved = pll_save_term_translations( array(
    'en' => $en_term_id,
    'fr' => $fr_term_id,
) );

pll_set_post_language() and pll_set_term_language() return true only when the assignment changed successfully. They return false if the object already has that language or if assignment fails. Do not treat false as a fatal error without checking current state.

Translatable type requirement

Post and term APIs only make sense for object types Polylang manages:

if ( ! pll_is_translated_post_type( get_post_type( $post_id ) ) ) {
    return;
}

$term = get_term( $term_id );
if ( $term instanceof WP_Term && ! pll_is_translated_taxonomy( $term->taxonomy ) ) {
    return;
}

Register custom CPTs/taxonomies for translation with pll_get_post_types or pll_get_taxonomies early. See polylang-language-api.

Media caveat

Attachments are translated only when Polylang media support is enabled. pll_get_post( $attachment_id, $lang ) still returns 0 if the attachment has no translation.

Do not duplicate attachment rows manually unless you also need all attachment metadata, file references, alt text, language, and translation group handling. Polylang's model has internal media translation behavior and fires pll_translate_media after creating a media translation.

Imports and migrations

Safe import order:

1. Ensure languages exist and collect explicit slugs.
2. Register CPT/taxonomy translation support before importing.
3. Insert original objects with pll_insert_post() or pll_insert_term().
4. Insert translations with translations arrays or link existing IDs with pll_save_*_translations().
5. Resolve relationship fields after all target translations exist.
6. Flush rewrite rules only if translated slugs or rewrite structures changed.

Do not rely on the current language during imports. Use explicit source and target slugs.

Hooks worth knowing

• pll_save_post fires after post language/translations are saved.
• pll_save_term fires after term language/translations are saved.
• pll_translate_media fires after media translation creation.
• pll_maybe_translate_term lets sync code substitute a term ID while copying taxonomy relations.

Hook only when you need to cooperate with Polylang's save/sync pipeline. Avoid recursive writes without a re-entry guard.

Common mistakes

• Saving translations before every object has a language.
• Comparing pll_get_post() result with false instead of checking > 0.
• Linking IDs from different post types or taxonomies into one translation group.
• Updating post_translations or term_translations term descriptions directly.
• Using get_term_by( 'slug', ... ) without lang => '' or without translating term IDs.
• Assuming a translated post's slug must be unique globally. Polylang Pro can share slugs by language.

Verification

Local source checked against:

• API wrappers and return values: wp-content/plugins/polylang/src/api.php
• Translation group storage and validation: src/translated-object.php
• Post type and post translation behavior: src/translated-post.php
• Term language, WXR group behavior, and term wrappers: src/translated-term.php

References

• Official documentation: https://polylang.pro/doc/function-reference/
• Official documentation: https://polylang.pro/doc/developpers-how-to/
• Verified source paths:
  • wp-content/plugins/polylang/src/api.php
  • wp-content/plugins/polylang/src/translated-object.php
  • wp-content/plugins/polylang/src/translated-post.php
  • wp-content/plugins/polylang/src/translated-term.php
  • wp-content/plugins/polylang/src/crud-posts.php
  • wp-content/plugins/polylang/src/crud-terms.php
  • wp-content/plugins/polylang/src/translatable-object.php