framework/i18n/GettextPoFile.php
public function save($filePath, $messages)
    {
        $language = str_replace('-', '_', basename(dirname($filePath)));
        $headers = [
            'msgid ""',
            'msgstr ""',
            '"Project-Id-Version: \n"',
            '"POT-Creation-Date: \n"',
            '"PO-Revision-Date: \n"',
            '"Last-Translator: \n"',
            '"Language-Team: \n"',
            '"Language: ' . $language . '\n"',
            '"MIME-Version: 1.0\n"',
            '"Content-Type: text/plain; charset=' . Yii::$app->charset . '\n"',
            '"Content-Transfer-Encoding: 8bit\n"',
        ];
        $content = implode("\n", $headers) . "\n\n";
        foreach ($messages as $id => $message) {
            $separatorPosition = strpos($id, chr(4));
            if ($separatorPosition !== false) {
                $content .= 'msgctxt "' . substr($id, 0, $separatorPosition) . "\"\n";
                $id = substr($id, $separatorPosition + 1);
            }
            $content .= 'msgid "' . $this->encode($id) . "\"\n";
            $content .= 'msgstr "' . $this->encode($message) . "\"\n\n";
        }
        file_put_contents($filePath, $content);
    }
public function save($filePath, $messages)
    {
        $language = str_replace('-', '_', basename(dirname($filePath)));
        $headers = [
            'msgid ""',
            'msgstr ""',
            '"Project-Id-Version: \n"',
            '"POT-Creation-Date: \n"',
            '"PO-Revision-Date: \n"',
            '"Last-Translator: \n"',
            '"Language-Team: \n"',
            '"Language: ' . $language . '\n"',
            '"MIME-Version: 1.0\n"',
            '"Content-Type: text/plain; charset=' . Yii::$app->charset . '\n"',
            '"Content-Transfer-Encoding: 8bit\n"',
        ];
        $content = implode("\n", $headers) . "\n\n";
        foreach ($messages as $id => $message) {
            $separatorPosition = strpos($id, chr(4));
            if ($separatorPosition !== false) {
                $content .= 'msgctxt "' . substr($id, 0, $separatorPosition) . "\"\n";
                $id = substr($id, $separatorPosition + 1);
            }
            $content .= 'msgid "' . $this->encode($id) . "\"\n";
            $content .= 'msgstr "' . $this->encode($message) . "\"\n\n";
        }
        file_put_contents($filePath, $content);
    }
Saves messages to a PO file.
@param string $filePath file path
@param array $messages message translations. Array keys are source messages and array values are
translated messages: source message => translated message. Note if the message has a context,
the message ID must be prefixed with the context with chr(4) as the separator.