How to translate a WordPress plugin in any language?

Question

I have completed my plugin, now want to provide a multilingual features for my users. I goggled about it, but it's hard to implement.

I've seen WordPress translation but need basic steps to follow and translate my plugin.

I have done these

1. downloaded POEdit.
2. created 'french.po' file in plugin dir
3. complied 'french.po' -> 'french.mo'

Need to do

1. How to define msgid & msgstr in po file?
2. How to load po/mo file in plugin?
3. How to replace labels/text through po/mo file?
4. how to use __e() & ___() to replace 'msgstr' in plugin pages?

Answer 1

With a plugin called, Codestyling Localization, you don't need to use POEdit.

I'll show you an example of using 'localizationsample' as the text domain. In this case, the language files are in the /lang/ directory. They don't need to be those names in your actual plugin; they are just examples.

Steps

1. Add these lines in the plugin comment header to be recognized by Codestyling Localization.

   Text Domain: localizationsample
   Domain Path: /lang

2. Create a directory named lang in your plugin directory.

3. Install and activate the Codestyling Localization plugin.

4. Go to Tools -> Localization

5. Find your plugin and click on Add New Language

6. Select the language (country) to localize in the radio button and press Create po-file At this point make sure a .po file is created in the lang folder.

7. Press Rescan -> scan now This is recommended since in my system without doing this, the plugin always shows an error saying "not all items are using the same text domain."

8. Press Edit This will bring you another page listing the messages available to be translated. Those messages are the ones passed to the functions __() and _e() in the plugin code.

9. Click on Edit in the table next to Copy then you'll get a dialog box to type your translation for each message. Finish translating.

10. Press generate mo-file At this point, you should see a .mo file being created in the lang folder.

11. Change your locale specified in wp-config.php to reflect the translation. The default is define('WPLANG', '');

Sample plugin

/*  
    Plugin Name: Sample Localization
    Description: Demonstrates how to localize your plugin.
    Text Domain: localizationsample
    Domain Path: /lang
*/

// Localization
add_action('init', 'localizationsample_init');
function localizationsample_init() {
    $path = dirname(plugin_basename( __FILE__ )) . '/lang/';
    $loaded = load_plugin_textdomain( 'localizationsample', false, $path);
    if ($_GET['page'] == basename(__FILE__) && !$loaded) {          
        echo '<div class="error">Sample Localization: ' . __('Could not load the localization file: ' . $path, 'localizationsample') . '</div>';
        return;
    } 
} 

// Add Admin Menu 
add_action('admin_menu','localizationsample_menu');
function localizationsample_menu() { 
    add_options_page(
        'Localization Demo',            // admin page title
        'Localization Demo',            // menu item name
        'manage_options',               // access privilege
        basename(__FILE__),                         // page slug for the option page
        'localization_demo_adminpanel'  // call-back function name
    );
}
function localization_demo_adminpanel() {

    echo '<div class="wrap"><div id="icon-themes" class="icon32"></div>';
    echo '<h2>' . __('Hi there!', 'localizationsample') . '</h2>'; 
    echo '<p>';
    _e('Hello world!', 'localizationsample');
    echo '</p>';
    echo '</div>'; // end of wrap
}

Answer 2

(THIS EXAMPLE IS A TRANSLATION to DEUTCH. YOU CAN CHANGE the customs to YOUR DESIRED names.)

in every plugins head, there is an unique name. (for example:

/*
Plugin Name: my-pluginname
.......
*/

then, in that plugin's folder, create a folder "languages";

then, into your plugin .php file (somewhere in the top), insert the initialization code:

class load_language 
{
    public function __construct()
    {
    add_action('init', array($this, 'load_my_transl'));
    }

     public function load_my_transl()
    {
        load_plugin_textdomain('my-pluginname', FALSE, dirname(plugin_basename(__FILE__)).'/languages/');
    }
}

$zzzz = new load_language;

then open any text editor, then insert like this code (NOTE, THAT we are only adding two sample messages, "hello" and "bye", so , you can ADD AS MANY messages AS YOU WANT with the similar lines).

# English translations for PACKAGE package.
# Copyright (C) 2012 THE PACKAGE'S COPYRIGHT HOLDER
# This file is distributed under the same license as the PACKAGE package.
# Automatically generated, 2012.
#
msgid ""
msgstr ""
"Project-Id-Version: my-pluginname 1.0\n"
"Report-Msgid-Bugs-To: \n"
"POT-Creation-Date: 2012-08-06 13:46-0400\n"
"PO-Revision-Date: 2013-03-21 11:20+0400\n"
"Last-Translator: Automatically generated\n"
"Language-Team: none\n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=utf-8\n"
"X-Poedit-SourceCharset: iso-8859-1\n"
"Content-Transfer-Encoding: 8bit\n"
"Plural-Forms: nplurals=2; plural=(n != 1);\n"
"X-Generator: Poedit 1.5.4\n"


#: mypluginindex.php:87 (it is just a line of a note, to remind where our code appears)
msgid "mymessage1"
msgstr "Hello"

#: mypluginindex.php:88
msgid "mymessage2"
msgstr "Bye"

then save this file as "my-pluginname-en_US.po" (note, that .po is an extension of file, so check that your text editor program has not saved to "my-pluginname-en_US.po.TXT").

then download POEDIT software, and open this file. then edit the "translation" field, and then save as "my-pluginname-de_DE" there will be generated two files ( If poEdit does not generate the second .mo file automatically, just go to File -> Preferences -> Editor and check the box that says "Automatically compile .mo file on save"),

then put those two file into "languages" folder.

after this, open wp-config.php and find this code:

define ('WPLANG, '');

and change to

define ('WPLANG, 'de_DE');

thats all. when wordperss is loaded, it will read your plugins language file, with prefix -de_DE.

so, in the plugin's .php file, instead of:

echo "Something string";

you should use:

echo __("mymessage1", 'my-pluginname');

Finished. Now you should test your plugin.
p.s.used links: https://codex.wordpress.org/I18n_for_WordPress_Developers
http://codex.wordpress.org/Translating_WordPress
https://codex.wordpress.org/Writing_a_Plugin
http://codex.wordpress.org/Installing_WordPress_in_Your_Language