O Guia Definitivo do Yii 1.1

Tip: The yiic tool in Yii can be used to manage message translations when
CPhpMessageSource is used as the message source. Its message command can
automatically extract messages to be translated from selected source files and merge
them with existing translations if necessary. For more details of using the message
command, please run yiic help message.
Starting from version 1.0.10, when using CPhpMessageSource to manage message
source, messages for an extension class (e.g. a widget, a module) can be specially
managed and used. In particular, if a message belongs to an extension whose class name
is Xyz, then the message category can be specified in the format of Xyz.categoryName.
The corresponding message file will be assumed to beBasePath/messages/LanguageID/
categoryName.php, where BasePath refers to the directory that contains the extension
class file. And when using Yii::t() to translate an extension message, the following format
should be used, instead:
Yii::t('Xyz.categoryName', 'message to be translated')
Since version 1.0.2, Yii has added the support for choice format. Choice format refers to
choosing a translated according to a given number value. For example, in English the
word 'book' may either take a singular form or a plural form depending on the number of
books, while in other languages, the word may not have different form (such as Chinese)
or may have more complex plural form rules (such as Russian). Choice format solves this
problem in a simple yet effective way.
To use choice format, a translated message must consist of a sequence of expressionmessage
pairs separated by |, as shown below
'expr1#message1|expr2#message2|expr3#message3'
where exprN refers to a valid PHP expression which evaluates to a boolean value
indicating whether the corresponding message should be returned. Only the message
corresponding to the first expression that evaluates to true will be returned. An expression
can contain a special variable named n (note, it is not $n) which will take the number value
passed as the first message parameter. For example, assuming a translated message is:
'n==1#one book|n>1#many books'
and we are passing a number value 2 in the message parameter array when calling Yii::t(),
we would obtain many books as the final translated message:
Yii::t('app', 'n==1#one book|n>1#many books', array(1)));
//or since 1.1.6
Yii::t('app', 'n==1#one book|n>1#many books', 1));
As a shortcut notation, if an expression is a number, it will be treated as n==Number.
Therefore, the above translated message can be also be written as: