What Are Functions in PHP?

Functions are an important part of the PHP programming language. They offer several advantages, including code reusability and modularity. They can help to make your programs more efficient by encapsulating a set of instructions into a self-contained unit that can be called as needed.

A function is a piece of code that you call within your script to execute a specific set of instructions. You can declare a function with the keyword function followed by the function name and a pair of parentheses. You can then provide input values to the function by specifying them as arguments.

The code that defines a function is executed once you call it, and the result of that execution is returned to the calling script. This way, the function can perform its task and return a result without re-executing any of the code in your program.

You can use a function to do a number of things, such as creating a list or reading a file. There are a number of built-in functions available, and you can create your own to do just about anything you need.

Functions can accept a variety of arguments, and these are passed to the function at the time of its call. In some cases, the value of a parameter can be changed once the function has been called. This is known as passing by reference. If you are using a variable in a function and want it to remain valid outside of the function, you should pass the value by reference by adding an ampersand (&) in front of the variable. This will cause a new entry to be added to the symbol table for the variable type and value.