How can php accurately determine the extension of a remote file?

How can php accurately determine the extension of a remote file? The http response header is as follows:
Array
(
[0] => HTTP/1.1 200 OK

[1] => Content-Length: 345942

[2] => Content-Type: application/octet-stream

[3] => Server: Microsoft-IIS/6.0

[4] => X-Powered-By: ASP. NET

[5] => Date: Sun, 08 Dec 2013 05:44:39 GMT

[6] => Connection: close

)

There is no extension in the file name, which is disorganized.

Reply to discussion (solution)

The file name is only used to identify the data block stored in the media.
In network communication, the file name is meaningless.

Since Content-Type: application/octet-stream has been declared as a stream
The Length of Content-Length: 345942 is not too large. you can analyze it as an image first.
All data streams use specific identification marks. someone sent code here in the previous stage. you can find out.

The file name is only used to identify the data block stored in the media.
In network communication, the file name is meaningless.

Since Content-Type: application/octet-stream has been declared as a stream
The Length of Content-Length: 345942 is not too large. you can analyze it as an image first.
All data streams use specific identification marks. someone sent code here in the previous stage. you can find out.

Content-Type: application/octet-stream, which corresponds to many types of files and is not unique. In addition, this file is in rar format. Not an image.

The file name is only used to identify the data block stored in the media.
In network communication, the file name is meaningless.

Since Content-Type: application/octet-stream has been declared as a stream
The Length of Content-Length: 345942 is not too large. you can analyze it as an image first.
All data streams use specific identification marks. someone sent code here in the previous stage. you can find out.

Content-Type: application/octet-stream, which corresponds to many types of files and is not unique. In addition, this file is in rar format. Not an image.

After finding the answer, it is the most reliable based on the file header.
Http://www.yc-edu.org/PHPpeixun/1233.html

Because the type is application/octet-stream
So you need to identify it yourself!
For self-recognition, you need to query the knowledge base based on feature words. There are thousands of common file types. you are willing to compare them one by one. I am not opposed to it.
The most common one is more than a dozen, and the check is much faster.

The characteristic character of the rar file is Rar.
The characteristic word of a jpg file is JFIF.
The characteristic word of a png file is PNG.
....

Because the type is application/octet-stream
So you need to identify it yourself!
For self-recognition, you need to query the knowledge base based on feature words. There are thousands of common file types. you are willing to compare them one by one. I am not opposed to it.
The most common one is more than a dozen, and the check is much faster.

The characteristic character of the rar file is Rar.
The characteristic word of a jpg file is JFIF.
The characteristic word of a png file is PNG.
....

What is self-recognition ??