使用PHP exec（）的Apache文件执行模型

Question

Newly registered user here after being a long time lurker!

I have an Apache 2.2 web server running on Windows locally (for now) as a service, with PHP 5 installed. I'm using PHP's exec() to run a command line client (.exe) hosted on the server, which authenticates the user to a database and makes pre-defined SQL queries on behalf of the user.

My question is: How does Apache run programs requested by multiple users through the (same) PHP exec() command? In this case, will Apache be using the same one instance of the client for all users who will access it, or will Apache be creating a new instance of the client for each user?

Since the client was designed for use by a single user, if Apache does reuse the same instance of a client, it will be running into a lot of concurrency issues.

I appreciate any help I can get, thanks!

Answer 1

PHP launches the process every time PHP calls exec(), and it keeps running for as long as it takes to finish. As such, you will end up with multiple copies of the process running at once if multiple users are simultaneously accessing scripts your web site which trigger it.

Unless you are using some really weird sort of database, there is probably a better way to query it than launching a command-line tool. If there's an ODBC driver available for your database, for instance, you may be able to use it directly via the PHP ODBC extension.