Is it possible to get the md5 of a file on a remote server? If so how?
how about md5_file("http://remotelocation/file")
It's not possible without downloading it, or the remote server providing the information (web service, HTML page, etc.)
You can use md5(file_get_contents("http://remotelocation/file")) to download the file and calculate the md5 hash if your PHP installation is configured to open remote streams. But that will download the complete file.
Well depends what you mean. There are two ways:
You connect to the remote server and calculate the hash there (like ssh to the server).
Get (download) the file and compute the hash.
Obviously to calculate the hash of a file you have to read the contents of the file.
来源：https://stackoverflow.com/questions/2304081/php-get-the-md5-of-remote-file