$re = '/(?:[^\|]\|)([^\|]+)(?:\|\|)/';
$str = 'машина|жигули, тойота, ваз, заз||техника|мясорубка, телевизор, телефон, Q123||фрукты|яблоко, апельсин, банан, анонс, маракуя1||';
$subst = "";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php