In PHP, a function is a reusable chunk of code that performs a specified task. It takes user input in the form of parameters, executes specified operations, and then outputs the results. When called, functions can either return values or just conduct an operation without returning anything.
User defined function.
Returning value function.
Internal (in-built) function.
There are approximately 700 functions in PHP that can be used for a variety of tasks.
A function is essentially a "chunk" of code that you may reuse instead of having to write it out many times. Programmers can use functions to break down or breakdown an issue into smaller pieces, each of which performs a specific purpose.
A function can be used over and over again once it has been defined. You can use the same function in your software multiple times, which saves you time. Imagine how much more difficult programming would be if you had to teach the computer about sines every time you needed to calculate the sine of an angle!