php 检查远程 URL 上是否存在图像
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Check whether image exists on remote URL
提问by Cristian Cotovan
I am generating dynamic URLs of images for book ISBNs. I need a reliable way with PHP to check whether the images actually exist at the remote url. I tried various approaches with different PHP libraries, curl, etc., but none of them works well, some of them are downright slow. Given the fact that I need to generate (and check!) about 60 URLS for each book in my database, this is a huge waiting time. Any clues?
我正在为图书 ISBN 生成图像的动态 URL。我需要一种可靠的 PHP 方法来检查图像是否确实存在于远程 url 中。我尝试了使用不同 PHP 库、curl 等的各种方法，但没有一个效果很好，其中一些非常慢。鉴于我需要为数据库中的每本书生成（并检查！）大约 60 个 URL，这是一个巨大的等待时间。有什么线索吗？
回答by dangkhoaweb
function checkRemoteFile($url)
{
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL,$url);
// don't download content
curl_setopt($ch, CURLOPT_NOBODY, 1);
curl_setopt($ch, CURLOPT_FAILONERROR, 1);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$result = curl_exec($ch);
curl_close($ch);
if($result !== FALSE)
{
return true;
}
else
{
return false;
}
}
--> that is the fastest way if your host supports curl
--> 如果您的主机支持 curl，这是最快的方式
回答by mohsin139
Use getimagesize() method like this
像这样使用 getimagesize() 方法
$external_link = ‘http://www.example.com/example.jpg';
if (@getimagesize($external_link)) {
echo “image exists “;
} else {
echo “image does not exist “;
}
回答by ChssPly76
There is no "easy" way here - at a very minimum, you need to generate a HEADrequest and check the resulting content type to make sure it's an image. That's not taking into account possible referrer issues. curl is the way to go here.
这里没有“简单”的方法——至少，您需要生成一个HEAD请求并检查生成的内容类型以确保它是一个图像。这没有考虑可能的推荐人问题。curl 是这里的方法。
回答by Andrew Deal
I have been doing this for my real estate picture tracking...
我一直在这样做是为了我的房地产图片跟踪...
$im = @imagecreatefromjpeg($pathtoimg);
if($im)
imagedestroy($im); // dont save, just ack...
elseif(!$missing[$inum])
$img404arr[] = $inum;
It 'seems' faster than downloading the actual image, taking about .3 seconds for each from images that avg 100k.
它“似乎”比下载实际图像要快，从平均 100k 的图像中下载每个图像大约需要 0.3 秒。
I wish I could just do a header check and read whether I get a 200 vs a 404 without downloading anything. Anyone have that handy?
我希望我可以只做一个标题检查并阅读我是否得到 200 与 404 而不下载任何东西。有谁用得着吗？
回答by Kevin Peno
You could use curl. Just set the curl option CURLOPT_NOBODY to true. This will skip body information and only get the head (thus http code as well). Then, you could use the CURLOPT_FAILONERROR to turn this whole process into a true/false type check
你可以使用curl。只需将 curl 选项 CURLOPT_NOBODY 设置为 true。这将跳过正文信息并只获取头部（因此也是 http 代码）。然后，您可以使用 CURLOPT_FAILONERROR 将整个过程转换为真/假类型检查
回答by timborden
回答by ChronoFish
It's probably moot at this point, but this works for me:
在这一点上可能没有实际意义，但这对我有用：
function is_webfile($webfile)
{
$fp = @fopen($webfile, "r");
if ($fp !== false)
fclose($fp);
return($fp);
}
回答by Gr Brainstorm
Solution from https://www.experts-exchange.com
来自https://www.experts-exchange.com 的解决方案
<?php
function url_exists($url) {
if (!$fp = curl_init($url)) return false;
return true;
}
?>
回答by kheengz
if(@getimagesize($remoteImageURL)){
//image exists!
}else{
//image does not exist.
}
回答by Jaimal Chohan
If the images all exist on the same remote server (or in the same network), you could run a web service on that server that will check the file system for the the image file and return a bool value indicating wheter the image exists or not.
如果图像都存在于同一个远程服务器（或在同一个网络中），您可以在该服务器上运行一个 Web 服务，该服务将检查图像文件的文件系统并返回一个布尔值，指示图像是否存在.
