An example of the built-in function, echo:
Hello, world!An example of a user-defined function, petName:
Sprinkles Eggert.An explanation of how functions work:
The concept of a function can be defined as a block of statements that can be repeated within a program. Programming complex tasks is easier with functions. PHP has a number of built-in functions for the purpose of creating dynamic websites with php sending data to the browser. User-defined functions are created by the user.