PHP exec（）无法访问.jar文件

Question

I'm setting up a form on my website. I want the PHP code that handles emailing info about the form to me to also run a java program printing information about it. Here is my PHP code

$name = $_POST['name']; 
$email_address = $_POST['email']; 
$date = $_POST['date'];
$time = $_POST['time'];
$message = $_POST['message']; 
$info = array($name, $email_address, $date, $time, $message);

exec('java -jar "C:\SomePathTo\HelloWorld.jar" $info 2>&1' , $output);`
var_dump($output);

And my Java code

public class HelloWorld {
    public static void main(String[] args) {
        for(int i = 0; i < args.length; i++) {
            System.out.println(args[i]);
        }
    }
}

When my website runs this code I get the following output/error message

array(1) { [0]=> string(197) "Error: Unable to access jarfile C:\SomePathTo\HelloWorld.jar" }

Help!

Answer 1

Obviously, the backslash escaping is not a problem, for the error message lists correct backslashes. If the problem was about backslashes, this would not be the case. (You used single quotes, which strips backslashes of their special meaning.)

Furthermore, we can notice that whatever generated the error message knows that it is looking for a "jarfile". What, in your stack, does that? It is not PHP; it is not the operating system's kernel. Apparently, you are getting Java VM to run. That's probably a good thing.

Why can't the Java VM access your jar file? You might have misspelt its name, but this would be something so obvious that it would have come up when you double-checked the code. It is more likely that this happens because the jar file is somewhere deep in your home directory (I can conclude "deep" from the fact that when you sanitised the filename, you kept the error message's length of 197) where the user context of the Java VM can't read. As you're running PHP through a web server, this would be determined by your web server's configuration, but it is fairly common to have a dedicated user account named something like "www-data" or "Internet Scripts" under which the code runs. You should find out which it is on your system.

Once that has been done, you have a few options. You can grant the user running your PHP (and in this context, Java VM) read access to the jar file. As soon as your jar file wants to access other files, you'll also need to let that user account to access those files, too. (Just make sure it can't overwrite or delete anything important.) Alternatively, you could reconfigure your web server (or ask your web server's administrator to it) so that it would run scripts written by you in your user context.