$subject = '你好啊，我是{abc}，我最爱看的电视是《{xyz}》';
$data = [
    'abc' => '小明',
    'xyz' => '还珠格格',
];

preg_match_all('|{.*}|U', $subject ,  $matches);
$result = $subject;
foreach ($matches[0] as $slot) {
    $key = substr($slot, 1, -1);
    $result = str_replace($slot, $data[$key] ?? '', $result);
}

echo $subject, "\n";
echo $result, "\n";