Functions

Define and call

A function wraps a named block of logic so it can run many times from many places. The function keyword names the block, and parentheses after the name run it. Define once at the top level, then call by name wherever the result is needed.

function greet() { echo "hello"; } greet();

Arguments and defaults

Parameters listed in the definition receive the arguments passed at the call site. A default value makes a parameter optional, and a type declaration rejects wrong input early with a clear error instead of a strange result deep inside the body.

function greet(string $name = "guest"): void { echo "hello " . $name; } greet("Ada"); greet();

Return values

The return statement sends a value back to the caller and ends the function at once. A function without return gives back null. Early returns for edge cases keep the main path flat and easy to follow.

function add(int $a, int $b): int { return $a + $b; } echo add(2, 3);

Reuse across files

Shared helpers live in their own file and load once with require_once, so every page uses the same tested code. See Call function from another file for the full walkthrough of defining in one file and calling from another.

require_once(__DIR__ . "/helpers.php"); echo slug("Hello World");

Next: Variable scope

Article author: Arthur Isaev