Introduction to User-Defined Functions

A user-defined function is a function that either you or another user has written and is not built into PHP itself. Built-in functions are generally faster than user-defined functions that do the same thing, as they are already compiled from C. Always look for built-in functions before you try to write your own!

Naming Functions

Naming things is difficult. Try to choose names for your functions that are descriptive but not overly long. Very long function names are unreadable. When you read the name, you should ideally be able to guess what the function does. The rules for naming identifiers in PHP apply here. Function names are case-insensitive; however, by convention, you do not call a function with casing that is different from how it was defined. Speaking of conventions, you are free to design the casing any way you like, but two flavors generally prevail: snake_case() or camelCase(). In all cases, do what your team agrees upon –...