<?PHP
$post_title  = "<!--:en-->English text<!--:--><!--:it-->Italian text<!--:-->";

$regexp = '/<\!--:(\w+?)-->([^<]+?)<\!--:-->/i';
if(preg_match_all($regexp,$post_title,$matches))
{
    $titles = array();
    $count = count($matches[0]);
    for($i = 0; $i < $count; $i++)
    {
        $titles[$matches[1][$i]] = $matches[2][$i];
    }
    PRint_r($titles);
}
else
{
    echo "No matches";
}
?>

打印：

Array
(
    [en] => English text
    [it] => Italian text
)