function URLIsValid($URL)
{
    $exists = true;
    $file_headers = @get_headers($URL);
    $InvalidHeaders = array('404', '403', '500');
    foreach($InvalidHeaders as $HeaderVal)
    {
            if(strstr($file_headers[0], $HeaderVal))
            {
                    $exists = false;
                    break;
            }
    }
    return $exists;
}

function URLIsValid($URL)
{
    $exists = true;
    $file_headers = @get_headers($URL);
    $InvalidHeaders = array('404', '403', '500');
    foreach($InvalidHeaders as $HeaderVal)
    {
            if(strstr($file_headers[0], $HeaderVal))
            {
                    $exists = false;
                    break;
            }
    }
    return $exists;
}

检查url是在线还是离线——

function get_http_response_code($theURL) {
    $headers = @get_headers($theURL);
    return substr($headers[0], 9, 3);
}

get_headers()返回一个数组，其中包含服务器响应HTTP请求时发送的报头。

$image_path = 'https://your-domain.com/assets/img/image.jpg';

$file_headers = @get_headers($image_path);
//Prints the response out in an array
//print_r($file_headers); 

if($file_headers[0] == 'HTTP/1.1 404 Not Found'){
   echo 'Failed because path does not exist.</br>';
}else{
   echo 'It works. Your good to go!</br>';
}

以上所有解决方案+额外的糖。(终极AIO解决方案)

/**
 * Check that given URL is valid and exists.
 * @param string $url URL to check
 * @return bool TRUE when valid | FALSE anyway
 */
function urlExists ( $url ) {
    // Remove all illegal characters from a url
    $url = filter_var($url, FILTER_SANITIZE_URL);

    // Validate URI
    if (filter_var($url, FILTER_VALIDATE_URL) === FALSE
        // check only for http/https schemes.
        || !in_array(strtolower(parse_url($url, PHP_URL_SCHEME)), ['http','https'], true )
    ) {
        return false;
    }

    // Check that URL exists
    $file_headers = @get_headers($url);
    return !(!$file_headers || $file_headers[0] === 'HTTP/1.1 404 Not Found');
}

例子:

var_dump ( urlExists('http://stackoverflow.com/') );
// Output: true;

我运行一些测试，看看我的网站上的链接是否有效-提醒我当第三方改变他们的链接。我有一个网站的问题，有一个配置不良的证书，这意味着php的get_headers不能工作。

所以，我读到卷曲更快，并决定给一个尝试。然后我在领英上遇到了一个问题，给了我一个999错误，后来证明是用户代理的问题。

我不关心证书是否对该测试无效，也不关心响应是否为重定向。

然后我认为使用get_headers无论如何，如果卷曲失败....

试试看....

/**
 * returns true/false if the $url is valid.
 *
 * @param string $url assumes this is a valid url.
 *
 * @return bool
 */
private function urlExists(string $url): bool
{
    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);     // do not output response in stdout
    curl_setopt($ch, CURLOPT_NOBODY, true);             // this does a head request to make it faster.
    curl_setopt($ch, CURLOPT_HEADER, true);             // just the headers
    curl_setopt($ch, CURLOPT_SSL_VERIFYSTATUS, false);  // turn off that pesky ssl stuff - some sys admins can't get it right.
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
    // set a real user agent to stop linkedin getting upset.
    curl_setopt($ch, CURLOPT_USERAGENT, 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.77 Safari/537.36');
    curl_exec($ch);
    $http_code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
    if (($http_code >= 200 && $http_code < 400) || $http_code === 999) {
        curl_close($ch);
        return true;
    }
    //$error = curl_error($ch); // used for debugging.
    curl_close($ch);

    // just try the get_headers - it might work!
    stream_context_set_default(
        ['http' => ['method' => 'HEAD']]
    );
    $file_headers = @get_headers($url);

    if ($file_headers !== false) {
        $response_code = substr($file_headers[0], 9, 3);
        return $response_code >= 200 && $response_code < 400;
    }

    return false;
}