PHPの変数の指定文字の定期置換_PHPチュートリアル

$str = preg_quote('(シルバー)');
$txt = '私のニックネーム (シルバー)';
echo preg_replace("/($str)/","$1",$txt);
?>

$str = quotemeta('(シルバー)');
$txt = '私のニックネーム (シルバー)';
echo preg_replace("/($str)/","$1",$txt);
?>

$text = “foobar123fooabcbar”;

$text = preg_replace(“/foo(?=bar)/”, “***”, $text);

$text = “foobar123fooabcbar”;

$text = preg_replace(“/(?<=bar)123/”, “***”, $text);

$text = “foobar123fooabcbar”;

$text = preg_replace(“/foo(?!bar)/”, “***”, $text);

$text = “foobar123fooabcbar”;

$text = preg_replace(“/(?