好的，这里有一些preg_match_all()的示例代码，它展示了如何删除嵌套：

$pattern = '(?:amsterdam|paris|zurich|munich|frankfurt|bulle)';
$result = preg_match_all($pattern, $subject, $matches);

# Check for errors in the pattern
if (false === $result) {
    throw new Exception(sprintf('Regular Expression failed: %s.', $pattern));
}

# Get the result, for your pattern that's the first element of $matches
$foundCities = $result ? $matches[0] : array();

printf("Found %d city/cities: %s.
", count($foundCitites), implode('; ', $foundCities));

由于$foundCities现在是一个简单的数组，您也可以直接迭代它：

foreach($foundCities as $index => $city) {
    echo $index, '. : ', $city, "
";
}

不需要嵌套循环，因为$matches返回值已经标准化。其概念是让代码在您需要进一步处理时返回/创建数据。