blocks|key|1067289|text|好的。发出一个仅包含报头的请求，并查找Content-Length报头。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1067290|entityMap^0|J|E|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

Sure. Make a headers-only request and look for the <code>Content-Length</code> header.

blocks|key|1282098|text|由于这个问题已经被标记为"+PHP“和"+Curl+"，我假设您知道如何在PHP中使用Curl。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1282099|如果您设置了curl_setopt(CURLOPT_NOBODY,+TRUE)，那么您将发出一个HEAD请求，并且可能会检查响应的"Content-Length“报头，这将只是header。|offset|length|style|CODE|1282100|entityMap^0|0|6|X|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@$D|L|E|M|F|G]]|9|@]|A|$]]|$1|H|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|I|$]]

Since this question is already tagged "php" and "curl", I'm assuming you know how to use Curl in PHP.

If you set <code>curl_setopt(CURLOPT_NOBODY, TRUE)</code> then you will make a HEAD request and can probably check the "Content-Length" header of the response, which will be only headers.

blocks|key|1067353|text|试试这段代码|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1067354|function+retrieve_remote_file_size($url){
+++++$ch+=+curl_init($url);

+++++curl_setopt($ch,+CURLOPT_RETURNTRANSFER,+TRUE);
+++++curl_setopt($ch,+CURLOPT_HEADER,+TRUE);
+++++curl_setopt($ch,+CURLOPT_NOBODY,+TRUE);

+++++$data+=+curl_exec($ch);
+++++$size+=+curl_getinfo($ch,+CURLINFO_CONTENT_LENGTH_DOWNLOAD);

+++++curl_close($ch);
+++++return+$size;
}|code-block|syntax|javascript|1067355|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Try this code

<pre><code>function retrieve_remote_file_size($url){
 $ch = curl_init($url);

 curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
 curl_setopt($ch, CURLOPT_HEADER, TRUE);
 curl_setopt($ch, CURLOPT_NOBODY, TRUE);

 $data = curl_exec($ch);
 $size = curl_getinfo($ch, CURLINFO_CONTENT_LENGTH_DOWNLOAD);

 curl_close($ch);
 return $size;
}
</code></pre>

blocks|key|1067374|text|尝试下面的函数来获取远程文件大小|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1067375|function+remote_file_size($url){
++++$head+=+"";
++++$url_p+=+parse_url($url);

++++$host+=+$url_p["host"];
++++if(!preg_match("/[0-9]*\.[0-9]*\.[0-9]*\.[0-9]*/",$host)){

++++++++$ip=gethostbyname($host);
++++++++if(!preg_match("/[0-9]*\.[0-9]*\.[0-9]*\.[0-9]*/",$ip)){

++++++++++++return+-1;
++++++++}
++++}
++++if(isset($url_p["port"]))
++++$port+=+intval($url_p["port"]);
++++else
++++$port++++=++++80;

++++if(!$port)+$port=80;
++++$path+=+$url_p["path"];

++++$fp+=+fsockopen($host,+$port,+$errno,+$errstr,+20);
++++if(!$fp)+{
++++++++return+false;
++++++++}+else+{
++++++++fputs($fp,+"HEAD+"++.+$url++.+"+HTTP/1.1\r\n");
++++++++fputs($fp,+"HOST:+"+.+$host+.+"\r\n");
++++++++fputs($fp,+"User-Agent:+http://www.example.com/my_application\r\n");
++++++++fputs($fp,+"Connection:+close\r\n\r\n");
++++++++$headers+=+"";
++++++++while+(!feof($fp))+{
++++++++++++$headers+.=+fgets+($fp,+128);
++++++++++++}
++++++++}
++++fclose+($fp);

++++$return+=+-2;
++++$arr_headers+=+explode("\n",+$headers);
++++foreach($arr_headers+as+$header)+{

++++++++$s1+=+"HTTP/1.1";
++++++++$s2+=+"Content-Length:+";
++++++++$s3+=+"Location:+";

++++++++if(substr(strtolower+($header),+0,+strlen($s1))+==+strtolower($s1))+$status+=+substr($header,+strlen($s1));
++++++++if(substr(strtolower+($header),+0,+strlen($s2))+==+strtolower($s2))+$size+++=+substr($header,+strlen($s2));
++++++++if(substr(strtolower+($header),+0,+strlen($s3))+==+strtolower($s3))+$newurl+=+substr($header,+strlen($s3));++
++++}

++++if(intval($size)+>+0)+{
++++++++$return=intval($size);
++++}+else+{
++++++++$return=$status;
++++}

++++if+(intval($status)==302+&&+strlen($newurl)+>+0)+{

++++++++$return+=+remote_file_size($newurl);
++++}
++++return+$return;
}|code-block|syntax|javascript|1067376|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Try the below function to get Remote file size

<pre><code>function remote_file_size($url){
 $head = "";
 $url_p = parse_url($url);

 $host = $url_p["host"];
 if(!preg_match("/[0-9]*\.[0-9]*\.[0-9]*\.[0-9]*/",$host)){

 $ip=gethostbyname($host);
 if(!preg_match("/[0-9]*\.[0-9]*\.[0-9]*\.[0-9]*/",$ip)){

 return -1;
 }
 }
 if(isset($url_p["port"]))
 $port = intval($url_p["port"]);
 else
 $port = 80;

 if(!$port) $port=80;
 $path = $url_p["path"];

 $fp = fsockopen($host, $port, $errno, $errstr, 20);
 if(!$fp) {
 return false;
 } else {
 fputs($fp, "HEAD " . $url . " HTTP/1.1\r\n");
 fputs($fp, "HOST: " . $host . "\r\n");
 fputs($fp, "User-Agent: http://www.example.com/my_application\r\n");
 fputs($fp, "Connection: close\r\n\r\n");
 $headers = "";
 while (!feof($fp)) {
 $headers .= fgets ($fp, 128);
 }
 }
 fclose ($fp);

 $return = -2;
 $arr_headers = explode("\n", $headers);
 foreach($arr_headers as $header) {

 $s1 = "HTTP/1.1";
 $s2 = "Content-Length: ";
 $s3 = "Location: ";

 if(substr(strtolower ($header), 0, strlen($s1)) == strtolower($s1)) $status = substr($header, strlen($s1));
 if(substr(strtolower ($header), 0, strlen($s2)) == strtolower($s2)) $size = substr($header, strlen($s2));
 if(substr(strtolower ($header), 0, strlen($s3)) == strtolower($s3)) $newurl = substr($header, strlen($s3)); 
 }

 if(intval($size) &gt; 0) {
 $return=intval($size);
 } else {
 $return=$status;
 }

 if (intval($status)==302 &amp;&amp; strlen($newurl) &gt; 0) {

 $return = remote_file_size($newurl);
 }
 return $return;
}
</code></pre>

blocks|key|1067415|text|最简单、最有效的实现：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1067416|function+remote_filesize($url,+$fallback_to_download+=+false)
{
++++static+$regex+=+'/%5EContent-Length:+*%2B\K\d%2B%2B$/im';
++++if+(!$fp+=+@fopen($url,+'rb'))+{
++++++++return+false;
++++}
++++if+(isset($http_response_header)+&&+preg_match($regex,+implode("\n",+$http_response_header),+$matches))+{
++++++++return+(int)$matches[0];
++++}
++++if+(!$fallback_to_download)+{
++++++++return+false;
++++}
++++return+strlen(stream_get_contents($fp));
}|code-block|syntax|javascript|1067417|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

The simplest and most efficient implementation:

<pre><code>function remote_filesize($url, $fallback_to_download = false)
{
 static $regex = '/^Content-Length: *+\K\d++$/im';
 if (!$fp = @fopen($url, 'rb')) {
 return false;
 }
 if (isset($http_response_header) &amp;&amp; preg_match($regex, implode("\n", $http_response_header), $matches)) {
 return (int)$matches[0];
 }
 if (!$fallback_to_download) {
 return false;
 }
 return strlen(stream_get_contents($fp));
}
</code></pre>

blocks|key|1282213|text|我不确定，但是你不能使用get_headers函数吗？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1282214|$url+++++=+'http://example.com/dir/file.txt';
$headers+=+get_headers($url,+true);

if+(+isset($headers['Content-Length'])+)+{
+++$size+=+'file+size:'+.+$headers['Content-Length'];
}
else+{
+++$size+=+'file+size:+unknown';
}

echo+$size;|code-block|syntax|javascript|1282215|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I'm not sure, but couldn't you use the get_headers function for this?

<pre><code>$url = 'http://example.com/dir/file.txt';
$headers = get_headers($url, true);

if ( isset($headers['Content-Length']) ) {
 $size = 'file size:' . $headers['Content-Length'];
}
else {
 $size = 'file size: unknown';
}

echo $size;
</code></pre>

blocks|key|1067569|text|这是另一种适用于不支持HEAD请求的服务器的方法。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1067570|它使用cURL向带有HTTP+range头部的内容发出请求，请求文件的第一个字节。|1067571|如果服务器支持范围请求(大多数媒体服务器都支持)，则它将接收具有资源大小的响应。|1067572|如果服务器没有响应字节范围，它将查找content-length报头来确定长度。|1067573|如果在range或content-length报头中找到该大小，则中止传输。如果找不到大小，并且函数开始读取响应正文，则传输将中止。|1067574|如果HEAD请求导致405+method+not+supported响应，这可能是一种补充方法。|1067575|/**
+*+Try+to+determine+the+size+of+a+remote+file+by+making+an+HTTP+request+for
+*+a+byte+range,+or+look+for+the+content-length+header+in+the+response.
+*+The+function+aborts+the+transfer+as+soon+as+the+size+is+found,+or+if+no
+*+length+headers+are+returned,+it+aborts+the+transfer.
+*
+*+@return+int%7Cnull+null+if+size+could+not+be+determined,+or+length+of+content
+*/
function+getRemoteFileSize($url)
{
++++$ch+=+curl_init($url);

++++$headers+=+array(
++++++++'Range:+bytes=0-1',
++++++++'Connection:+close',
++++);

++++$in_headers+=+true;
++++$size+++++++=+null;

++++curl_setopt($ch,+CURLOPT_HEADER,+1);
++++curl_setopt($ch,+CURLOPT_RETURNTRANSFER,+1);
++++curl_setopt($ch,+CURLOPT_USERAGENT,+'Mozilla/5.0+(Windows+NT+6.1;+WOW64)+AppleWebKit/537.36+(KHTML,+like+Gecko)+Chrome/46.0.2450.0+Iron/46.0.2450.0');
++++curl_setopt($ch,+CURLOPT_HTTPHEADER,+$headers);
++++curl_setopt($ch,+CURLOPT_SSL_VERIFYHOST,+0);
++++curl_setopt($ch,+CURLOPT_SSL_VERIFYPEER,+0);
++++curl_setopt($ch,+CURLOPT_VERBOSE,+0);+//+set+to+1+to+debug
++++curl_setopt($ch,+CURLOPT_STDERR,+fopen('php://output',+'r'));

++++curl_setopt($ch,+CURLOPT_HEADERFUNCTION,+function($curl,+$line)+use+(&$in_headers,+&$size)+{
++++++++$length+=+strlen($line);

++++++++if+(trim($line)+==+'')+{
++++++++++++$in_headers+=+false;
++++++++}

++++++++list($header,+$content)+=+explode(':',+$line,+2);
++++++++$header+=+strtolower(trim($header));

++++++++if+($header+==+'content-range')+{
++++++++++++//+found+a+content-range+header
++++++++++++list($rng,+$s)+=+explode('/',+$content,+2);
++++++++++++$size+=+(int)$s;
++++++++++++return+0;+//+aborts+transfer
++++++++}+else+if+($header+==+'content-length'+&&+206+!=+curl_getinfo($curl,+CURLINFO_HTTP_CODE))+{
++++++++++++//+found+content-length+header+and+this+is+not+a+206+Partial+Content+response+(range+response)
++++++++++++$size+=+(int)$content;
++++++++++++return+0;
++++++++}+else+{
++++++++++++//+continue
++++++++++++return+$length;
++++++++}
++++});

++++curl_setopt($ch,+CURLOPT_WRITEFUNCTION,+function($curl,+$data)+use+($in_headers)+{
++++++++if+(!$in_headers)+{
++++++++++++//+shouldn't+be+here+unless+we+couldn't+determine+file+size
++++++++++++//+abort+transfer
++++++++++++return+0;
++++++++}

++++++++//+write+function+is+also+called+when+reading+headers
++++++++return+strlen($data);
++++});

++++$result+=+curl_exec($ch);
++++$info+++=+curl_getinfo($ch);

++++return+$size;
}|code-block|syntax|javascript|1067576|用法：|1067577|$size+=+getRemoteFileSize('http://example.com/video.mp4');
if+($size+===+null)+{
++++echo+"Could+not+determine+file+size+from+headers.";
}+else+{
++++echo+"File+size+is+{$size}+bytes.";
}|1067578|entityMap^0|B|4|0|0|0|0|0|2|4|A|3|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|13|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|14|8|@]|D|@]|E|$]]|$1|J|3|K|5|6|7|15|8|@]|D|@]|E|$]]|$1|L|3|M|5|6|7|16|8|@]|D|@]|E|$]]|$1|N|3|O|5|6|7|17|8|@$9|18|A|19|B|C]|$9|1A|A|1B|B|C]]|D|@]|E|$]]|$1|P|3|Q|5|R|7|1C|8|@]|D|@]|E|$S|T]]|$1|U|3|V|5|6|7|1D|8|@]|D|@]|E|$]]|$1|W|3|X|5|R|7|1E|8|@]|D|@]|E|$S|T]]|$1|Y|3|-4|5|6|7|1F|8|@]|D|@]|E|$]]]|Z|$]]

Here is another approach that will work with servers that do not support <code>HEAD</code> requests.

It uses cURL to make a request for the content with an HTTP range header asking for the first byte of the file.

If the server supports range requests (most media servers will) then it will receive the response with the size of the resource.

If the server does not response with a byte range, it will look for a content-length header to determine the length.

If the size is found in a range or content-length header, the transfer is aborted. If the size is not found and the function starts reading the response body, the transfer is aborted.

This could be a supplementary approach if a <code>HEAD</code> request results in a <code>405</code> method not supported response.

<pre><code>/**
 * Try to determine the size of a remote file by making an HTTP request for
 * a byte range, or look for the content-length header in the response.
 * The function aborts the transfer as soon as the size is found, or if no
 * length headers are returned, it aborts the transfer.
 *
 * @return int|null null if size could not be determined, or length of content
 */
function getRemoteFileSize($url)
{
 $ch = curl_init($url);

 $headers = array(
 'Range: bytes=0-1',
 'Connection: close',
 );

 $in_headers = true;
 $size = null;

 curl_setopt($ch, CURLOPT_HEADER, 1);
 curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
 curl_setopt($ch, CURLOPT_USERAGENT, 'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/46.0.2450.0 Iron/46.0.2450.0');
 curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
 curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
 curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
 curl_setopt($ch, CURLOPT_VERBOSE, 0); // set to 1 to debug
 curl_setopt($ch, CURLOPT_STDERR, fopen('php://output', 'r'));

 curl_setopt($ch, CURLOPT_HEADERFUNCTION, function($curl, $line) use (&amp;$in_headers, &amp;$size) {
 $length = strlen($line);

 if (trim($line) == '') {
 $in_headers = false;
 }

 list($header, $content) = explode(':', $line, 2);
 $header = strtolower(trim($header));

 if ($header == 'content-range') {
 // found a content-range header
 list($rng, $s) = explode('/', $content, 2);
 $size = (int)$s;
 return 0; // aborts transfer
 } else if ($header == 'content-length' &amp;&amp; 206 != curl_getinfo($curl, CURLINFO_HTTP_CODE)) {
 // found content-length header and this is not a 206 Partial Content response (range response)
 $size = (int)$content;
 return 0;
 } else {
 // continue
 return $length;
 }
 });

 curl_setopt($ch, CURLOPT_WRITEFUNCTION, function($curl, $data) use ($in_headers) {
 if (!$in_headers) {
 // shouldn't be here unless we couldn't determine file size
 // abort transfer
 return 0;
 }

 // write function is also called when reading headers
 return strlen($data);
 });

 $result = curl_exec($ch);
 $info = curl_getinfo($ch);

 return $size;
}
</code></pre>

Usage:

<pre><code>$size = getRemoteFileSize('http://example.com/video.mp4');
if ($size === null) {
 echo "Could not determine file size from headers.";
} else {
 echo "File size is {$size} bytes.";
}
</code></pre>

blocks|key|1282307|text|一行最佳解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1282308|echo+array_change_key_case(get_headers("http://.../file.txt",1))['content-length'];|code-block|syntax|javascript|1282309|php太美味了|1282310|function+urlsize($url):int{
+++return+array_change_key_case(get_headers($url,1))['content-length'];
}

echo+urlsize("http://.../file.txt");|1282311|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

one line best solution :

<pre><code>echo array_change_key_case(get_headers("http://.../file.txt",1))['content-length'];
</code></pre>

php is too delicius

<pre><code>function urlsize($url):int{
 return array_change_key_case(get_headers($url,1))['content-length'];
}

echo urlsize("http://.../file.txt");
</code></pre>

blocks|key|1067656|text|试试这个:我用过了，效果很好。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1067657|++++function+getRemoteFilesize($url)
{
++++$file_headers+=+@get_headers($url,+1);
++++if($size+=getSize($file_headers)){
return+$size;
++++}+elseif($file_headers[0]+==+"HTTP/1.1+302+Found"){
++++++++if+(isset($file_headers["Location"]))+{
++++++++++++$url+=+$file_headers["Location"][0];
++++++++++++if+(strpos($url,+"/_as/")+!==+false)+{
++++++++++++++++$url+=+substr($url,+0,+strpos($url,+"/_as/"));
++++++++++++}
++++++++++++$file_headers+=+@get_headers($url,+1);
++++++++++++return+getSize($file_headers);
++++++++}
++++}
++++return+false;
}

function+getSize($file_headers){

++++if+(!$file_headers+%7C%7C+$file_headers[0]+==+"HTTP/1.1+404+Not+Found"+%7C%7C+$file_headers[0]+==+"HTTP/1.0+404+Not+Found")+{
++++++++return+false;
++++}+elseif+($file_headers[0]+==+"HTTP/1.0+200+OK"+%7C%7C+$file_headers[0]+==+"HTTP/1.1+200+OK")+{

++++++++$clen=(isset($file_headers['Content-Length']))?$file_headers['Content-Length']:false;
++++++++$size+=+$clen;
++++++++if($clen)+{
++++++++++++switch+($clen)+{
++++++++++++++++case+$clen+<+1024:
++++++++++++++++++++$size+=+$clen+.+'+B';
++++++++++++++++++++break;
++++++++++++++++case+$clen+<+1048576:
++++++++++++++++++++$size+=+round($clen+/+1024,+2)+.+'+KiB';
++++++++++++++++++++break;
++++++++++++++++case+$clen+<+1073741824:
++++++++++++++++++++$size+=+round($clen+/+1048576,+2)+.+'+MiB';
++++++++++++++++++++break;
++++++++++++++++case+$clen+<+1099511627776:
++++++++++++++++++++$size+=+round($clen+/+1073741824,+2)+.+'+GiB';
++++++++++++++++++++break;
++++++++++++}
++++++++}
++++++++return+$size;

++++}
++++return+false;
}|code-block|syntax|javascript|1067658|现在，像这样测试：|1067659|echo+getRemoteFilesize('http://mandasoy.com/wp-content/themes/spacious/images/plain.png').PHP_EOL;
echo+getRemoteFilesize('http://bookfi.net/dl/201893/e96818').PHP_EOL;
echo+getRemoteFilesize('https://stackoverflow.com/questions/14679268/downloading-files-as-attachment-filesize-incorrect').PHP_EOL;|1067660|结果：|1067661|24.82+KiB|1067662|912+KiB|1067663|101.85+KiB|1067664|entityMap^0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|Y|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|Z|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|10|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|11|8|@]|9|@]|A|$]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

Try this: I use it and got good result.

<pre><code> function getRemoteFilesize($url)
{
 $file_headers = @get_headers($url, 1);
 if($size =getSize($file_headers)){
return $size;
 } elseif($file_headers[0] == "HTTP/1.1 302 Found"){
 if (isset($file_headers["Location"])) {
 $url = $file_headers["Location"][0];
 if (strpos($url, "/_as/") !== false) {
 $url = substr($url, 0, strpos($url, "/_as/"));
 }
 $file_headers = @get_headers($url, 1);
 return getSize($file_headers);
 }
 }
 return false;
}

function getSize($file_headers){

 if (!$file_headers || $file_headers[0] == "HTTP/1.1 404 Not Found" || $file_headers[0] == "HTTP/1.0 404 Not Found") {
 return false;
 } elseif ($file_headers[0] == "HTTP/1.0 200 OK" || $file_headers[0] == "HTTP/1.1 200 OK") {

 $clen=(isset($file_headers['Content-Length']))?$file_headers['Content-Length']:false;
 $size = $clen;
 if($clen) {
 switch ($clen) {
 case $clen &lt; 1024:
 $size = $clen . ' B';
 break;
 case $clen &lt; 1048576:
 $size = round($clen / 1024, 2) . ' KiB';
 break;
 case $clen &lt; 1073741824:
 $size = round($clen / 1048576, 2) . ' MiB';
 break;
 case $clen &lt; 1099511627776:
 $size = round($clen / 1073741824, 2) . ' GiB';
 break;
 }
 }
 return $size;

 }
 return false;
}
</code></pre>

Now, test like these:

<pre><code>echo getRemoteFilesize('http://mandasoy.com/wp-content/themes/spacious/images/plain.png').PHP_EOL;
echo getRemoteFilesize('http://bookfi.net/dl/201893/e96818').PHP_EOL;
echo getRemoteFilesize('https://stackoverflow.com/questions/14679268/downloading-files-as-attachment-filesize-incorrect').PHP_EOL;
</code></pre>

Results:

24.82 KiB

912 KiB

101.85 KiB

blocks|key|1282413|text|为了覆盖HTTP/2请求，这里提供的函数https://stackoverflow.com/a/2602624/2380767需要稍微修改一下：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1282414|<?php
/**
+*+Returns+the+size+of+a+file+without+downloading+it,+or+-1+if+the+file
+*+size+could+not+be+determined.
+*
+*+@param+$url+-+The+location+of+the+remote+file+to+download.+Cannot
+*+be+null+or+empty.
+*
+*+@return+The+size+of+the+file+referenced+by+$url,+or+-1+if+the+size
+*+could+not+be+determined.
+*/
function+curl_get_file_size(+$url+)+{
++//+Assume+failure.
++$result+=+-1;

++$curl+=+curl_init(+$url+);

++//+Issue+a+HEAD+request+and+follow+any+redirects.
++curl_setopt(+$curl,+CURLOPT_NOBODY,+true+);
++curl_setopt(+$curl,+CURLOPT_HEADER,+true+);
++curl_setopt(+$curl,+CURLOPT_RETURNTRANSFER,+true+);
++curl_setopt(+$curl,+CURLOPT_FOLLOWLOCATION,+true+);
++curl_setopt(+$curl,+CURLOPT_USERAGENT,+get_user_agent_string()+);

++$data+=+curl_exec(+$curl+);
++curl_close(+$curl+);

++if(+$data+)+{
++++$content_length+=+"unknown";
++++$status+=+"unknown";

++++if(+preg_match(+"/%5EHTTP\/1\.[01]+(\d\d\d)/",+$data,+$matches+)+)+{
++++++$status+=+(int)$matches[1];
++++}+elseif(+preg_match(+"/%5EHTTP\/2+(\d\d\d)/",+$data,+$matches+)+)+{
++++++$status+=+(int)$matches[1];
++++}

++++if(+preg_match(+"/Content-Length:+(\d%2B)/",+$data,+$matches+)+)+{
++++++$content_length+=+(int)$matches[1];
++++}+elseif(+preg_match(+"/content-length:+(\d%2B)/",+$data,+$matches+)+)+{
++++++++$content_length+=+(int)$matches[1];
++++}

++++//+http://en.wikipedia.org/wiki/List_of_HTTP_status_codes
++++if(+$status+==+200+%7C%7C+($status+>+300+&&+$status+<=+308)+)+{
++++++$result+=+$content_length;
++++}
++}

++return+$result;
}
?>|code-block|syntax|javascript|1282415|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/2602624/2380767^0|K|17|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

To cover the HTTP/2 request, the function provided here <a href="https://stackoverflow.com/a/2602624/2380767">https://stackoverflow.com/a/2602624/2380767</a> needs to be changed a bit:

<pre><code>&lt;?php
/**
 * Returns the size of a file without downloading it, or -1 if the file
 * size could not be determined.
 *
 * @param $url - The location of the remote file to download. Cannot
 * be null or empty.
 *
 * @return The size of the file referenced by $url, or -1 if the size
 * could not be determined.
 */
function curl_get_file_size( $url ) {
 // Assume failure.
 $result = -1;

 $curl = curl_init( $url );

 // Issue a HEAD request and follow any redirects.
 curl_setopt( $curl, CURLOPT_NOBODY, true );
 curl_setopt( $curl, CURLOPT_HEADER, true );
 curl_setopt( $curl, CURLOPT_RETURNTRANSFER, true );
 curl_setopt( $curl, CURLOPT_FOLLOWLOCATION, true );
 curl_setopt( $curl, CURLOPT_USERAGENT, get_user_agent_string() );

 $data = curl_exec( $curl );
 curl_close( $curl );

 if( $data ) {
 $content_length = "unknown";
 $status = "unknown";

 if( preg_match( "/^HTTP\/1\.[01] (\d\d\d)/", $data, $matches ) ) {
 $status = (int)$matches[1];
 } elseif( preg_match( "/^HTTP\/2 (\d\d\d)/", $data, $matches ) ) {
 $status = (int)$matches[1];
 }

 if( preg_match( "/Content-Length: (\d+)/", $data, $matches ) ) {
 $content_length = (int)$matches[1];
 } elseif( preg_match( "/content-length: (\d+)/", $data, $matches ) ) {
 $content_length = (int)$matches[1];
 }

 // http://en.wikipedia.org/wiki/List_of_HTTP_status_codes
 if( $status == 200 || ($status &gt; 300 &amp;&amp; $status &lt;= 308) ) {
 $result = $content_length;
 }
 }

 return $result;
}
?&gt;
</code></pre>

blocks|key|1282464|text|如果您使用的是laravel+7+<=|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1282465|use+Illuminate\Support\Facades\Http;

Http::head($url)->header('Content-Length');|code-block|syntax|javascript|1282466|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

If you using laravel 7 &lt;=
<pre class="lang-php prettyprint-override"><code>use Illuminate\Support\Facades\Http;

Http::head($url)-&gt;header('Content-Length');
</code></pre>

Is there a way to get the size of a remote file <a href="http://my_url/my_file.txt" rel="noreferrer">http://my_url/my_file.txt</a> without downloading the file?

Remote file size without downloading file

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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有没有一种方法可以在不下载文件的情况下获得远程文件的大小？

问不下载文件的远程文件大小
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