Hello, welcome back! Today, we'll explore "Optional/Default Parameters" in PHP. This approach helps maintain backward compatibility when updating or enhancing your software, much like upgrading a toy car without removing its existing features.

Today's journey includes:

• Uncovering the concept of optional/default parameters in PHP.
• Understanding their role in maintaining backward compatibility.
• Applying default parameters to practical problems.

Let's dive in!

First, let's decipher how optional/default parameters work and how they aid in backward compatibility. In PHP, functions can have parameters with default values. This allows the function to be called with fewer arguments, which ensures older ways of calling the function remain functional even after enhancements.

Imagine a greet function that initially just greeted a person by their name. Later, we can include a message if needed, without breaking the original function:

In this example, the greet function provides options to only use the name or to also include a message. The older invocation greet($name) remains valid, ensuring backward compatibility.