在foreach循环中使用cURL(php)

我有许多HTTPS-URLS,我必须在其中找到特殊短语,因此我试图在foreach循环中使用cURL,但是它不起作用.

...
foreach($sites as $site) {

    $URL = $site;        

    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);

    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
    curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);

    $response = curl_exec($ch);
    curl_close($ch);

}

print substr($response, $start, $i);
...

如果仅使用一个HTTPS-URL,则会得到该短语,但是在foreach循环中却无法正常工作.
有人能帮我吗？ (：

请原谅我的英语不好.

解决方法:

这可能有帮助:)将结果存储在数组中

$sites = ['https://stackoverflow.com','http://example.org'];
$result = [];
foreach ($sites as $site) {

    $ch = curl_init();

    curl_setopt($ch, CURLOPT_URL, $site);

    // User agent
    curl_setopt($ch, CURLOPT_USERAGENT, "PHP Curl");

    // Include header in result? (0 = yes, 1 = no)
    curl_setopt($ch, CURLOPT_HEADER, 0);

    // Should cURL return or print out the data? (true = return, false = print)
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

    // Timeout in seconds
    curl_setopt($ch, CURLOPT_TIMEOUT, 10);

    // execute the given URL, and return output
    $result[] = curl_exec($ch);

    curl_close($ch);


}

var_dump($result);