Аккуратнее! Код этот портит Яндекс.Карты. Плагин "Oi Yandex Maps for WordPress"!
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This goes in the PHP in your functions.php file.
Once done, you can use the [raw] shortcode in your posts: [raw]Unformatted code[/raw]

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function my_formatter($content) {
$new_content = '';
$pattern_full = '{(∖[raw∖].*?∖[/raw∖])}is';
$pattern_contents = '{∖[raw∖](.*?)∖[/raw∖]}is';
$pieces = preg_split($pattern_full, $content, -1, PREG_SPLIT_DELIM_CAPTURE);

foreach ($pieces as $piece) {
if (preg_match($pattern_contents, $piece, $matches)) {
$new_content .= $matches[1];
} else {
$new_content .= wptexturize(wpautop($piece));
}
}

return $new_content;
}

remove_filter('the_content', 'wpautop');
remove_filter('the_content', 'wptexturize');

add_filter('the_content', 'my_formatter', 99);