PHP, or Hypertext Preprocessor, is a widely-used server-side scripting language designed specifically for web development. As a fundamental component of dynamic web development, PHP enables developers to create interactive and data-driven websites that can respond to user inputs in real-time. Unlike static HTML pages, which deliver the same content to every user, PHP allows for the customization of content based on various factors such as user credentials, location, and preferences. By embedding PHP code within HTML, developers can seamlessly integrate dynamic content into their sites, providing a richer user experience.

One of the reasons PHP remains the backbone of dynamic web development is its extensive support for various databases, such as MySQL, PostgreSQL, and MongoDB. This compatibility makes it easier for developers to store and manage large volumes of data, making PHP an ideal choice for content management systems (CMS) and e-commerce platforms. Furthermore, the language benefits from an active global community, ensuring continuous improvements and a wealth of resources, tutorials, and frameworks that facilitate versatile and efficient dynamic web applications development.

Choosing the right framework can significantly enhance a developer's productivity and efficiency. When it comes to PHP frameworks, there are numerous options available. However, not all frameworks are created equal. Here are the top 10 PHP frameworks every developer should know, which can help streamline the development process and improve application performance.

1. Laravel - Known for its elegant syntax, Laravel offers a robust set of features including routing, sessions, caching, and authentication, making it a top choice among developers.
2. Symfony - A highly flexible framework, Symfony is perfect for large-scale enterprise applications, providing reusable components and a strong community support.
3. CodeIgniter - Lightweight and straightforward, CodeIgniter is known for its small footprint and exceptional performance.
4. Yii - Featuring a powerful caching system, Yii is ideal for building high-performance web applications.
5. Zend Framework - Now known as Laminas, this framework is enterprise-ready and offers a cohesive set of components designed for extensive web applications.
6. FuelPHP - A flexible, modular framework that supports the MVC architectural pattern, FuelPHP gives developers immense flexibility.
7. CakePHP - Known for its rapid development capabilities, CakePHP simplifies the building process with its code generation and scaffolding features.
8. Phalcon - Uniquely implemented as a C extension, Phalcon provides an unparalleled performance boost, making it an excellent choice for high-speed applications.
9. Laravel Lumen - A micro-framework tailored for building APIs, Lumen is a lightweight option for quickly creating services without the overhead.
10. Slim - Another micro-framework that excels in simplicity, Slim is perfect for small web applications and APIs.

Optimizing PHP code for better performance involves several key strategies. Start by leveraging built-in functions, as they are typically more efficient than custom implementations. For instance, instead of writing a manual looping structure to process arrays, use PHP's built-in functions like array_map, array_filter, and array_reduce. Additionally, consider utilizing opcache, a powerful PHP extension that caches the compiled bytecode of PHP scripts, reducing the overhead of parsing and compiling on every request.

Another important aspect of PHP optimization is minimizing database interactions. You can achieve this by employing techniques such as query caching, which stores the results of frequently run queries, and batch processing, which allows you to execute multiple queries in a single call. Furthermore, always ensure that your code practices proper error handling and profiling to identify bottlenecks. Employ tools like Xdebug to analyze performance and pinpoint areas that require improvement.