.. index::
single: Translation; Message Format
How to Translate Messages using the ICU MessageFormat
=====================================================
Messages (i.e. strings) in applications are almost never completely static.
They contain variables or other complex logic like pluralization. In order to
handle this, the Translator component supports the `ICU MessageFormat`_ syntax.
.. tip::
You can test out examples of the ICU MessageFormatter in this `online editor`_.
Using the ICU Message Format
----------------------------
In order to use the ICU Message Format, the message domain has to be
suffixed with ``+intl-icu``:
====================== ===============================
Normal file name ICU Message Format filename
====================== ===============================
``messages.en.yaml`` ``messages+intl-icu.en.yaml``
``messages.fr_FR.xlf`` ``messages+intl-icu.fr_FR.xlf``
``admin.en.yaml`` ``admin+intl-icu.en.yaml``
====================== ===============================
All messages in this file will now be processed by the
:phpclass:`MessageFormatter` during translation.
.. _component-translation-placeholders:
Message Placeholders
--------------------
The basic usage of the MessageFormat allows you to use placeholders (called
*arguments* in ICU MessageFormat) in your messages:
.. configuration-block::
.. code-block:: yaml
# translations/messages+intl-icu.en.yaml
say_hello: 'Hello {name}!'
.. code-block:: xml
say_helloHello {name}!
.. code-block:: php
// translations/messages+intl-icu.en.php
return [
'say_hello' => "Hello {name}!",
];
.. caution::
With the previous format, placeholders were often named between ``%``. This
character is no longer valid with the ICU MessageFormat syntax. Be careful
to rename your parameters.
Everything within the curly braces (``{...}``) is processed by the formatter
and replaced by its placeholder::
// prints "Hello Fabien!"
echo $translator->trans('say_hello', ['name' => 'Fabien']);
// prints "Hello Symfony!"
echo $translator->trans('say_hello', ['name' => 'Symfony']);
Selecting Different Messages Based on a Condition
-------------------------------------------------
The curly brace syntax allows to "modify" the output of the variable. One of
these functions is the ``select`` function. It acts like PHP's `switch statement`_
and allows to use different strings based on the value of the variable. A
typical usage of this is gender:
.. configuration-block::
.. code-block:: yaml
# translations/messages+intl-icu.en.yaml
invitation_title: >-
{organizer_gender, select,
female {{organizer_name} has invited you for her party!}
male {{organizer_name} has invited you for his party!}
other {{organizer_name} have invited you for their party!}
}
.. code-block:: xml
invitation_title{organizer_gender, select,
female {{organizer_name} has invited you for her party!}
male {{organizer_name} has invited you for his party!}
other {{organizer_name} have invited you for their party!}
}
.. code-block:: php
// translations/messages+intl-icu.en.php
return [
'invitation_title' => '{organizer_gender, select,
female {{organizer_name} has invited you for her party!}
male {{organizer_name} has invited you for his party!}
other {{organizer_name} have invited you for their party!}
}',
];
This might look very complex. The basic syntax for all functions is
``{variable_name, function_name, function_statement}`` (where, as you see
later, ``function_statement`` is optional for some functions). In this case,
the function name is ``select`` and its statement contains the "cases" of this
select. This function is applied over the ``organizer_gender`` variable::
// prints "Ryan has invited you for his party!"
echo $translator->trans('invitation_title', [
'organizer_name' => 'Ryan',
'organizer_gender' => 'male',
]);
// prints "John & Jane have invited you for their party!"
echo $translator->trans('invitation_title', [
'organizer_name' => 'John & Jane',
'organizer_gender' => 'not_applicable',
]);
The ``{...}`` syntax alternates between "literal" and "code" mode. This allows
you to use literal text in the select statements:
#. The first ``{organizer_gender, select, ...}`` block starts the "code" mode,
which means ``organizer_gender`` is processed as a variable.
#. The inner ``{... has invited you for her party!}`` block brings you back in
"literal" mode, meaning the text is not processed.
#. Inside this block, ``{organizer_name}`` starts "code" mode again, allowing
``organizer_name`` to be processed as variable.
.. tip::
While it might seem more logical to only put ``her``, ``his`` or ``their``
in the switch statement, it is better to use "complex arguments" at the
outermost structure of the message. The strings are in this way better
readable for translators and, as you can see in the ``other`` case, other
parts of the sentence might be influenced by the variables.
.. _component-translation-pluralization:
Pluralization
-------------
Another interesting function is ``plural``. It allows you to
handle pluralization in your messages (e.g. ``There are 3 apples`` vs
``There is one apple``). The function looks very similar to the ``select`` function:
.. configuration-block::
.. code-block:: yaml
# translations/messages+intl-icu.en.yaml
num_of_apples: >-
{apples, plural,
=0 {There are no apples}
one {There is one apple...}
other {There are # apples!}
}
.. code-block:: xml
num_of_apples{apples, plural, =0 {There are no apples} one {There is one apple...} other {There are # apples!}}
.. code-block:: php
// translations/messages+intl-icu.en.php
return [
'num_of_apples' => '{apples, plural,
=0 {There are no apples}
one {There is one apple...}
other {There are # apples!}
}',
];
Pluralization rules are actually quite complex and differ for each language.
For instance, Russian uses different plural forms for numbers ending with 1;
numbers ending with 2, 3 or 4; numbers ending with 5, 6, 7, 8 or 9; and even
some exceptions of this!
In order to properly translate this, the possible cases in the ``plural``
function are also different for each language. For instance, Russian has
``one``, ``few``, ``many`` and ``other``, while English has only ``one`` and
``other``. The full list of possible cases can be found in Unicode's
`Language Plural Rules`_ document. By prefixing with ``=``, you can match exact
values (like ``0`` in the above example).
Usage of this string is the same as with variables and select::
// prints "There is one apple..."
echo $translator->trans('num_of_apples', ['apples' => 1]);
// prints "There are 23 apples!"
echo $translator->trans('num_of_apples', ['apples' => 23]);
.. note::
You can also set an ``offset`` variable to determine whether the
pluralization should be offset (e.g. in sentences like ``You and # other people``
/ ``You and # other person``).
.. tip::
When combining the ``select`` and ``plural`` functions, try to still have
``select`` as outermost function:
.. code-block:: text
{gender_of_host, select,
female {
{num_guests, plural, offset:1
=0 {{host} does not give a party.}
=1 {{host} invites {guest} to her party.}
=2 {{host} invites {guest} and one other person to her party.}
other {{host} invites {guest} and # other people to her party.}}
}
male {
{num_guests, plural, offset:1
=0 {{host} does not give a party.}
=1 {{host} invites {guest} to his party.}
=2 {{host} invites {guest} and one other person to his party.}
other {{host} invites {guest} and # other people to his party.}}
}
other {
{num_guests, plural, offset:1
=0 {{host} does not give a party.}
=1 {{host} invites {guest} to their party.}
=2 {{host} invites {guest} and one other person to their party.}
other {{host} invites {guest} and # other people to their party.}}
}
}
.. sidebar:: Using Ranges in Messages
The pluralization in the legacy Symfony syntax could be used with custom
ranges (e.g. have a different messages for 0-12, 12-40 and 40+). The ICU
message format does not have this feature. Instead, this logic should be
moved to PHP code::
// Instead of
$message = $translator->trans('balance_message', $balance);
// with a message like:
// ]-Inf,0]Oops! I'm down|]0,1000]I still have money|]1000,Inf]I have lots of money
// use three different messages for each range:
if ($balance < 0) {
$message = $translator->trans('no_money_message');
} elseif ($balance < 1000) {
$message = $translator->trans('some_money_message');
} else {
$message = $translator->trans('lots_of_money_message');
}
Additional Placeholder Functions
--------------------------------
Besides these, the ICU MessageFormat comes with a couple other interesting functions.
Ordinal
~~~~~~~
Similar to ``plural``, ``selectordinal`` allows you to use numbers as ordinal scale:
.. configuration-block::
.. code-block:: yaml
# translations/messages+intl-icu.en.yaml
finish_place: >-
You finished {place, selectordinal,
one {#st}
two {#nd}
few {#rd}
other {#th}
}!
# when only formatting the number as ordinal (like above), you can also
# use the `ordinal` function:
finish_place: You finished {place, ordinal}!
.. code-block:: xml
finish_placeYou finished {place, selectordinal, one {#st} two {#nd} few {#rd} other {#th}}!finish_placeYou finished {place, ordinal}!
.. code-block:: php
// translations/messages+intl-icu.en.php
return [
'finish_place' => 'You finished {place, selectordinal,
one {#st}
two {#nd}
few {#rd}
other {#th}
}!',
// when only formatting the number as ordinal (like above), you can
// also use the `ordinal` function:
'finish_place' => 'You finished {place, ordinal}!',
];
.. code-block:: php
// prints "You finished 1st!"
echo $translator->trans('finish_place', ['place' => 1]);
// prints "You finished 9th!"
echo $translator->trans('finish_place', ['place' => 9]);
// prints "You finished 23rd!"
echo $translator->trans('finish_place', ['place' => 23]);
The possible cases for this are also shown in Unicode's `Language Plural Rules`_ document.
Date and Time
~~~~~~~~~~~~~
The date and time function allows you to format dates in the target locale
using the :phpclass:`IntlDateFormatter`:
.. configuration-block::
.. code-block:: yaml
# translations/messages+intl-icu.en.yaml
published_at: 'Published at {publication_date, date} - {publication_date, time, short}'
.. code-block:: xml
published_atPublished at {publication_date, date} - {publication_date, time, short}
.. code-block:: php
// translations/messages+intl-icu.en.php
return [
'published_at' => 'Published at {publication_date, date} - {publication_date, time, short}',
];
The "function statement" for the ``time`` and ``date`` functions can be one of
``short``, ``medium``, ``long`` or ``full``, which correspond to the
`constants defined by the IntlDateFormatter class`_::
// prints "Published at Jan 25, 2019 - 11:30 AM"
echo $translator->trans('published_at', ['publication_date' => new \DateTime('2019-01-25 11:30:00')]);
Numbers
~~~~~~~
The ``number`` formatter allows you to format numbers using Intl's :phpclass:`NumberFormatter`:
.. configuration-block::
.. code-block:: yaml
# translations/messages+intl-icu.en.yaml
progress: '{progress, number, percent} of the work is done'
value_of_object: 'This artifact is worth {value, number, currency}'
.. code-block:: xml
progress{progress, number, percent} of the work is donevalue_of_objectThis artifact is worth {value, number, currency}
.. code-block:: php
// translations/messages+intl-icu.en.php
return [
'progress' => '{progress, number, percent} of the work is done',
'value_of_object' => 'This artifact is worth {value, number, currency}',
];
.. code-block:: php
// prints "82% of the work is done"
echo $translator->trans('progress', ['progress' => 0.82]);
// prints "100% of the work is done"
echo $translator->trans('progress', ['progress' => 1]);
// prints "This artifact is worth $9,988,776.65"
// if we would translate this to i.e. French, the value would be shown as
// "9 988 776,65 €"
echo $translator->trans('value_of_object', ['value' => 9988776.65]);
.. _`online editor`: http://format-message.github.io/icu-message-format-for-translators/
.. _`ICU MessageFormat`: http://userguide.icu-project.org/formatparse/messages
.. _`switch statement`: https://www.php.net/control-structures.switch
.. _`Language Plural Rules`: http://www.unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html
.. _`constants defined by the IntlDateFormatter class`: https://www.php.net/manual/en/class.intldateformatter.php