Accessing content from the tpl language, or PHP api should automatically return the localized/translated data, if translations were setup beforehand. The chosen language/locale are conditioned by the current siteaccess' settings, in site.ini (the respective override placed in the your siteaccess directory : settings/siteaccess/<siteaccessname>/site.ini.append.php), under RegionalSettings.
The default, english eZ Flow one looks like this :
More information on configuring eZ Publish for nice localisations : http://doc.ez.no/eZ-Publish/Technical-manual/4.x/Reference/Configuration-files/site.ini/RegionalSettings
Cheers !
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Nicolas Pastorino
Director Community - eZ
Member of the Community Project Board