PHP, which stands for Hypertext Preprocessor, is a highly popular, versatile server-side scripting language that's primarily used for web development. Companies require this tech skill as it forms the backbone of many web services as it can be easily embedded in HTML files and HTML codes, eliminating the need for separate coding required for each function. PHP scripts are used to enhance web page functions, manage databases, and even produce graphical images dynamically.

Mastering PHP requires a good understanding of not only the PHP programming language itself which includes concepts like control structures, arrays, error handling, and form handling, but also a strong understanding of web development basics. Professionals skilled in PHP can create, customize, and maintain websites and web applications, making them valuable assets in organizations of all sizes - from startups to large tech enterprises.

To learn PHP, a thorough understanding of HTML and CSS is a must, as these form the foundational building blocks of web programming. Knowledge of JavaScript and SQL (Structured Query Language) will also be beneficial considering PHP often works in conjunction with these languages in the backend.

Understanding the basics of programming logic and having problem-solving abilities can strongly support your journey of learning PHP. Those seeking to master PHP should also familiarize themselves with PHP frameworks such as Laravel, CodeIgniter, or Symfony. Such frameworks not only escalate development speed but also provide well-organized, reusable and maintainable code.

Qualification in related subjects, like computer science or information technology, provides a solid foundation for a career involving PHP. However, with dedication, practice, and the wealth of resources available, both online and offline, learning PHP can be self-driven as well.

In many job roles, candidates with experience or understanding of Content Management Systems (like WordPress, Drupal, or Joomla) which use PHP quite extensively may be preferred. Lastly, just like any other technology, the tech world expects PHP professionals to stay abreast with the ongoing updates and advancements like PHP 7 and PHP 8 to stay competitive.