Declaring & Calling Functions

So far, you've been writing code that runs from top to bottom. But as your programs grow, you'll find yourself repeating the same code in multiple places. Functions solve this problem by letting you group code into reusable blocks.

A function is a named block of code that performs a specific task. You define it once, then call it whenever you need that task done. In PHP, you declare a function using the function keyword:

<?php
function sayHello() {
    echo "Hello, World!\n";
}
?>

This creates a function named sayHello. The code inside the curly braces is the function body—it defines what happens when the function runs.

However, declaring a function doesn't execute it. To run the code inside, you need to call the function by using its name followed by parentheses:

<?php
function sayHello() {
    echo "Hello, World!\n";
}

sayHello();
sayHello();
?>

This outputs:

Hello, World!
Hello, World!

Each time you call sayHello(), PHP executes the code inside the function. You can call a function as many times as you need, which is what makes functions so powerful for avoiding repetition.