Question
Answer and Explanation
The difference between libphp5-zts.so and libphp5.so (or simply libphp5, the extension might vary depending on the system) lies in their support for thread safety. These two libraries represent different ways PHP is compiled to handle concurrent requests in web server environments.
Here's a breakdown:
1. libphp5.so (or libphp5):
- This library represents a standard PHP installation that is not thread-safe. This version of PHP is usually used with web servers that operate on a process-per-request model, such as the traditional CGI (Common Gateway Interface) or mod_php for Apache.
- In a non-thread-safe setup, each web request is handled by a separate process. This means each request is isolated, preventing potential data corruption from race conditions. However, this also means that starting new processes can be resource-intensive and make it less efficient when dealing with a high number of concurrent users.
- For web servers using the non-thread-safe version of PHP, the web server typically manages concurrency via multiple child processes (e.g., Apache prefork module).
2. libphp5-zts.so:
- The -zts suffix indicates that this library is the "Zend Thread Safe" version of PHP. It's designed to handle multiple requests within the same process, by using threads, rather than relying only on multiple processes.
- This version is suitable for use with web servers that support a threaded model such as Apache’s worker or event MPM (Multi-Processing Module). This is much more efficient as threads are “lighter” than separate processes, leading to better resource usage and a faster response to simultaneous requests.
- Thread safety in this context means that PHP has been compiled with mechanisms to avoid data corruption when multiple threads access and modify the same shared memory locations.
Key Differences Summarized:
- Thread Safety: libphp5-zts.so is thread-safe while libphp5.so is not.
- Concurrency Model: libphp5-zts.so is designed for threaded web servers, whereas libphp5.so is for process-based web servers.
- Efficiency: The threaded version typically provides better performance and lower resource consumption under high concurrent traffic.
- Compatibility: The correct PHP library must be paired with the appropriate web server and MPM (Multi-Processing Module) configuration.
Which one to use?
- If you are using Apache with mod_php, a prefork MPM and a non-threaded PHP version (libphp5 or just libphp5.so) is generally more suitable.
- If you are using Apache with mod_php and want to use worker or event MPMs , or using FastCGI with web servers like Nginx, then a thread-safe version of PHP (libphp5-zts.so or alike) will be required.
In conclusion, the choice between the two libraries depends heavily on your web server setup and concurrency requirements. Choosing the correct library for the configuration of your server can lead to increased performance and a more stable system.