Call to undefined function __()

[reeait]

Premetto che conosco ben poco il PHP.

Sto lavorando su un tema per WordPress e vorrei modificare una stringa per adattarla alla traduzione (avendo un file POT/PO a disposizione).

Tale stringa si presenta così:

{
if ($send)
echo '<div class="column col-2"><h2>Your message has been sent!</h2><div class="confirm">
<p class="textconfirm">Thank you for contacting us.
We will get back to you within 2 business days.</p>
</div></div>';
else
echo '<div class="column col-2"><h2>Oops!</h2><div class="confirm">
<p class="texterror">Due to an unknown error, your form was not submitted, please resubmit it or try later.</p>
<code>'.$buffer.'</code>
</div></div>'; 
} 

Per la mia traduzione l'ho fatta diventare così:

{
if ($send)
echo '<div class="column col-2"><h2>' . __('Your message has been sent!', 'miotema') . '<div class="confirm">
<p class="textconfirm">Thank you for contacting us.
We will get back to you within 2 business days.</p>
</div></div>';
else
echo '<div class="column col-2"><h2>Oops!</h2><div class="confirm">
<p class="texterror">Due to an unknown error, your form was not submitted, please resubmit it or try later.</p>
<code>'.$buffer.'</code>
</div></div>'; 
} 

Quindi il "Your message has been sent!" l'ho fatto diventare

' . __('Your message has been sent!', 'miotema') . ' 

E siccome sto sbagliando qualcosa mi viene fuori questo errore:

Fatal error: Call to undefined function __() in /home/miosito/public_html/wp-content/themes/miotema/file.php on line 89

Mi sembra un errore comune ma non riesco a venirne a capo.

[piero.mac]

perche' se __ e' una stringa e non la metti tra apici viene scambiata per una funzione.

Cos'e' __ ????

[reeait]

Guarda, qui spiega come predisporre un tema WordPress per la traduzione:
http://codex.wordpress.org/Translating_WordPress

Cito solo una parte:

WordPress's developers chose to use the GNU gettext localization framework to provide localization infrastructure to WordPress. gettext is a mature, widely used framework for modular translation of software, and is the de facto standard for localization in the open source/free software realm.

gettext uses message-level translation — that is, every "message" displayed to users is translated individually, whether it be a paragraph or a single word. In WordPress, such "messages" are generated, translated, and used by the WordPress PHP files via two PHP functions. __() is used when the message is passed as an argument to another function; _e() is used to write the message directly to the page. More detail on these two functions:

__($message)
Searches the localization module for the translation of $message, and passes the translation to the PHP return statement. If no translation is found for $message, it just returns $message.
_e($message)
Searches the localization module for the translation of $message, and passes the translation to the PHP echo statement. If no translation is found for $message, it just echoes $message.

Quindi se avessi avuto del semplice HTML tipo:

<div>Your message has been sent!</div>

, la mia traduzione sarebbe diventata effettiva con questo codice:

<div><?php _e('Your message has been sent!') ?></div>

Invece (se ho capito bene), dentro un codice PHP dovrei usare sto __() .

[reeait]

PS.
In definitva __() è una funzione PHP.