我正在自学一些基本的抓取,我发现有时我输入代码的 URL 会返回 404,这会破坏我的所有其他代码。
所以我需要在代码顶部进行测试,以检查 URL 是否返回 404。
这似乎是一项非常简单的任务,但谷歌没有给我任何答案。我担心我在寻找错误的东西。
一个博客推荐我用这个:
$valid = @fsockopen($url, 80, $errno, $errstr, 30);
然后测试 $valid 是否为空。
但是我认为给我带来问题的 URL 上有一个重定向,所以 $valid 对于所有值都是空的。或者我做错了什么。
我也研究过“head request”,但我还没有找到任何我可以玩或尝试的实际代码示例。
建议? curl 是怎么回事?
curl
绑定,您可以使用 curl_getinfo
检查错误代码,如下所示:
$handle = curl_init($url);
curl_setopt($handle, CURLOPT_RETURNTRANSFER, TRUE);
/* Get the HTML or whatever is linked in $url. */
$response = curl_exec($handle);
/* Check for 404 (file not found). */
$httpCode = curl_getinfo($handle, CURLINFO_HTTP_CODE);
if($httpCode == 404) {
/* Handle 404 here. */
}
curl_close($handle);
/* Handle $response here. */
如果你运行的是 php5,你可以使用:
$url = 'http://www.example.com';
print_r(get_headers($url, 1));
或者使用 php4,用户贡献了以下内容:
/**
This is a modified version of code from "stuart at sixletterwords dot com", at 14-Sep-2005 04:52. This version tries to emulate get_headers() function at PHP4. I think it works fairly well, and is simple. It is not the best emulation available, but it works.
Features:
- supports (and requires) full URLs.
- supports changing of default port in URL.
- stops downloading from socket as soon as end-of-headers is detected.
Limitations:
- only gets the root URL (see line with "GET / HTTP/1.1").
- don't support HTTPS (nor the default HTTPS port).
*/
if(!function_exists('get_headers'))
{
function get_headers($url,$format=0)
{
$url=parse_url($url);
$end = "\r\n\r\n";
$fp = fsockopen($url['host'], (empty($url['port'])?80:$url['port']), $errno, $errstr, 30);
if ($fp)
{
$out = "GET / HTTP/1.1\r\n";
$out .= "Host: ".$url['host']."\r\n";
$out .= "Connection: Close\r\n\r\n";
$var = '';
fwrite($fp, $out);
while (!feof($fp))
{
$var.=fgets($fp, 1280);
if(strpos($var,$end))
break;
}
fclose($fp);
$var=preg_replace("/\r\n\r\n.*\$/",'',$var);
$var=explode("\r\n",$var);
if($format)
{
foreach($var as $i)
{
if(preg_match('/^([a-zA-Z -]+): +(.*)$/',$i,$parts))
$v[$parts[1]]=$parts[2];
}
return $v;
}
else
return $var;
}
}
}
两者都会有类似的结果:
Array
(
[0] => HTTP/1.1 200 OK
[Date] => Sat, 29 May 2004 12:28:14 GMT
[Server] => Apache/1.3.27 (Unix) (Red-Hat/Linux)
[Last-Modified] => Wed, 08 Jan 2003 23:11:55 GMT
[ETag] => "3f80f-1b6-3e1cb03b"
[Accept-Ranges] => bytes
[Content-Length] => 438
[Connection] => close
[Content-Type] => text/html
)
因此您可以检查标题响应是否正常,例如:
$headers = get_headers($url, 1);
if ($headers[0] == 'HTTP/1.1 200 OK') {
//valid
}
if ($headers[0] == 'HTTP/1.1 301 Moved Permanently') {
//moved or redirect page
}
使用strager的代码,还可以查看CURLINFO_HTTP_CODE中的其他代码。有些网站不报告 404,而只是重定向到自定义 404 页面并返回 302(重定向)或类似内容。我用它来检查服务器上是否存在实际文件(例如 robots.txt)。很明显,这种文件如果存在就不会导致重定向,但如果不存在,它将重定向到 404 页面,正如我之前所说,它可能没有 404 代码。
function is_404($url) {
$handle = curl_init($url);
curl_setopt($handle, CURLOPT_RETURNTRANSFER, TRUE);
/* Get the HTML or whatever is linked in $url. */
$response = curl_exec($handle);
/* Check for 404 (file not found). */
$httpCode = curl_getinfo($handle, CURLINFO_HTTP_CODE);
curl_close($handle);
/* If the document has loaded successfully without any redirection or error */
if ($httpCode >= 200 && $httpCode < 300) {
return false;
} else {
return true;
}
}
正如 strager 所建议的,研究使用 cURL。您可能也有兴趣使用 curl_setopt 设置 CURLOPT_NOBODY 以跳过下载整个页面(您只需要标题)。
如果您正在寻找一个最简单的解决方案,并且您可以在 php5 上一次尝试这个解决方案
file_get_contents('www.yoursite.com');
//and check by echoing
echo $http_response_header[0];
此函数通过使用 HEAD 请求返回 PHP 中 URL 的状态代码,而无需下载正文(html 代码):
function isHttpStatusCode200(string $url): bool
{
return getHttpResponseCode($url) === 200;
}
function getHttpResponseCode(string $url): int
{
$context = stream_context_create(
array(
'http' => array(
'method' => 'HEAD'
)
)
);
$headers = get_headers($url, false, $context);
return substr($headers[0], 9, 3);
}
例子:
echo isHttpStatusCode200('https://www.google.com');
//displays: true
if(($twitter_XML_raw=file_get_contents($timeline))==false){
// Retrieve HTTP status code
list($version,$status_code,$msg) = explode(' ',$http_response_header[0], 3);
// Check the HTTP Status code
switch($status_code) {
case 200:
$error_status="200: Success";
break;
case 401:
$error_status="401: Login failure. Try logging out and back in. Password are ONLY used when posting.";
break;
case 400:
$error_status="400: Invalid request. You may have exceeded your rate limit.";
break;
case 404:
$error_status="404: Not found. This shouldn't happen. Please let me know what happened using the feedback link above.";
break;
case 500:
$error_status="500: Twitter servers replied with an error. Hopefully they'll be OK soon!";
break;
case 502:
$error_status="502: Twitter servers may be down or being upgraded. Hopefully they'll be OK soon!";
break;
case 503:
$error_status="503: Twitter service unavailable. Hopefully they'll be OK soon!";
break;
default:
$error_status="Undocumented error: " . $status_code;
break;
}
本质上,您使用“文件获取内容”方法来检索 URL,它会自动使用状态代码填充 http 响应标头变量。
如果 url 没有返回 200 OK,这会给你 true
function check_404($url) {
$headers=get_headers($url, 1);
if ($headers[0]!='HTTP/1.1 200 OK') return true; else return false;
}
附录;考虑性能测试了这 3 种方法。
结果,至少在我的测试环境中:
卷曲获胜
这个测试是在只需要headers(noBody)的情况下进行的。 测试自己:
$url = "http://de.wikipedia.org/wiki/Pinocchio";
$start_time = microtime(TRUE);
$headers = get_headers($url);
echo $headers[0]."<br>";
$end_time = microtime(TRUE);
echo $end_time - $start_time."<br>";
$start_time = microtime(TRUE);
$response = file_get_contents($url);
echo $http_response_header[0]."<br>";
$end_time = microtime(TRUE);
echo $end_time - $start_time."<br>";
$start_time = microtime(TRUE);
$handle = curl_init($url);
curl_setopt($handle, CURLOPT_RETURNTRANSFER, TRUE);
curl_setopt($handle, CURLOPT_NOBODY, 1); // and *only* get the header
/* Get the HTML or whatever is linked in $url. */
$response = curl_exec($handle);
/* Check for 404 (file not found). */
$httpCode = curl_getinfo($handle, CURLINFO_HTTP_CODE);
// if($httpCode == 404) {
// /* Handle 404 here. */
// }
echo $httpCode."<br>";
curl_close($handle);
$end_time = microtime(TRUE);
echo $end_time - $start_time."<br>";
这是一个简短的解决方案。
$handle = curl_init($uri);
curl_setopt($handle, CURLOPT_RETURNTRANSFER, TRUE);
curl_setopt($handle,CURLOPT_HTTPHEADER,array ("Accept: application/rdf+xml"));
curl_setopt($handle, CURLOPT_NOBODY, true);
curl_exec($handle);
$httpCode = curl_getinfo($handle, CURLINFO_HTTP_CODE);
if($httpCode == 200||$httpCode == 303)
{
echo "you might get a reply";
}
curl_close($handle);
在您的情况下,您可以将
application/rdf+xml
更改为您使用的任何内容。
作为公认答案的额外提示:
使用建议解决方案的变体时,由于 php 设置“max_execution_time”而出现错误。所以我做了以下事情:
set_time_limit(120);
$curl = curl_init($url);
curl_setopt($curl, CURLOPT_NOBODY, true);
$result = curl_exec($curl);
set_time_limit(ini_get('max_execution_time'));
curl_close($curl);
首先我将时间限制设置为更高的秒数,最后我将其设置回 php 设置中定义的值。
<?php
$url= 'www.something.com';
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_HEADER, true);
curl_setopt($ch, CURLOPT_NOBODY, true);
curl_setopt($ch, CURLOPT_USERAGENT, "Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.0.3) Gecko/2008092417 Firefox/3.0.4");
curl_setopt($ch, CURLOPT_RETURNTRANSFER,1);
curl_setopt($ch, CURLOPT_TIMEOUT,10);
curl_setopt($ch, CURLOPT_ENCODING, "gzip");
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
$output = curl_exec($ch);
$httpcode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
curl_close($ch);
echo $httpcode;
?>
您也可以使用此代码查看任何链接的状态:
<?php
function get_url_status($url, $timeout = 10)
{
$ch = curl_init();
// set cURL options
$opts = array(CURLOPT_RETURNTRANSFER => true, // do not output to browser
CURLOPT_URL => $url, // set URL
CURLOPT_NOBODY => true, // do a HEAD request only
CURLOPT_TIMEOUT => $timeout); // set timeout
curl_setopt_array($ch, $opts);
curl_exec($ch); // do it!
$status = curl_getinfo($ch, CURLINFO_HTTP_CODE); // find HTTP status
curl_close($ch); // close handle
echo $status; //or return $status;
//example checking
if ($status == '302') { echo 'HEY, redirection';}
}
get_url_status('http://yourpage.comm');
?>
这里有办法!
<?php
$url = "http://www.google.com";
if(@file_get_contents($url)){
echo "Url Exists!";
} else {
echo "Url Doesn't Exist!";
}
?>
这个简单的脚本只是向 URL 请求其源代码。如果请求成功完成,它会输出“URL Exists!”。如果不存在,它会输出“URL 不存在!”。
这只是一段代码, 希望对你有用
$ch = @curl_init();
@curl_setopt($ch, CURLOPT_URL, 'http://example.com');
@curl_setopt($ch, CURLOPT_USERAGENT, "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.1) Gecko/20061204 Firefox/2.0.0.1");
@curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
@curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
@curl_setopt($ch, CURLOPT_TIMEOUT, 10);
$response = @curl_exec($ch);
$errno = @curl_errno($ch);
$error = @curl_error($ch);
$response = $response;
$info = @curl_getinfo($ch);
return $info['http_code'];