Common PHP development bugs can lead to significant issues in web applications, causing frustration for developers and users alike. One of the most prevalent bugs is the undefined variable error. This occurs when a variable is used before it is defined, often resulting in unexpected behavior or warnings. To fix this, developers should ensure that all variables are properly initialized before use, or utilize the isset() function to check if a variable is set.

Another frequent issue is the SQL injection vulnerability, which can compromise the security of an application. This bug arises when user input is directly included in SQL queries without proper sanitization. To mitigate this risk, developers should utilize prepared statements with parameterized queries, which separate SQL logic from data, thus enhancing security. Additionally, consistently validating and sanitizing user input is essential to prevent vulnerabilities from arising.

As a PHP developer, implementing essential features in your applications can significantly enhance performance and user experience. Firstly, consider adopting error handling mechanisms. This includes using exceptions and custom error pages to ensure that issues are addressed without compromising the user experience. Additionally, implementing input validation is critical to safeguarding against SQL injection and other vulnerabilities. Use built-in functions like filter_var() and regularly sanitize user inputs.

Another critical feature is maintaining robust security protocols. This involves using techniques like password hashing with password_hash() and ensuring secure session management. Furthermore, establishing a structured database interaction pattern, such as using PDO for database access, promotes flexibility and security in your data operations. Lastly, incorporating unit testing practices early in the development process not only streamlines validation but also enhances code maintainability in the long run.

As we delve into 2023, the question of whether PHP is still relevant in the ever-evolving landscape of web development arises. Despite the emergence of numerous programming languages and frameworks, PHP continues to power a significant portion of the internet. According to various statistics, over 77% of websites using a server-side language rely on PHP. This widespread use is sustained by its lightweight nature, versatility, and the strong community that contributes to a rich ecosystem of libraries and frameworks, such as Laravel and Symfony.

Current trends indicate that PHP is adapting to the modern demands of developers. The introduction of PHP 8 brought features like JIT compilation and improvements in type safety, making the language more efficient and user-friendly. Additionally, the rise of PHP frameworks helps developers implement robust solutions with less effort, paving the way for better performance and scalability. Thus, while challenges from JavaScript frameworks and newer languages are notable, the adaptability and ongoing enhancements of PHP suggest that it remains a relevant choice for sustainable web development in 2023.