What is a PHP function?

A function in PHP is a reusable block of code that performs a specific task. Define with the function keyword: function greet(string $name): string { return "Hello, $name!"; }. PHP functions support default parameter values, type declarations (PHP 7+), and return type declarations. PHP passes arguments by value by default — to pass by reference, prefix the parameter with &: function increment(int &$n): void { $n++; }. PHP also has variable functions (storing a function name in a variable and calling it), anonymous functions (closures), and arrow functions (PHP 7.4+). Functions are globally scoped by default in PHP.