Defining functions

Learn to define functions with the function keyword.

Defining functions

A function is a block of code that performs a task and can be run whenever you want. In PHP a function starts with the function keyword, followed by a name, parentheses and a body in curly braces.

Example: function greet() { echo "Hello"; }. Here greet is the function name; the parentheses are empty for now and the body uses echo to print a message. Defining a function does not run it; it waits to be called.

Function body and naming

Function names must start with a letter or underscore; they cannot start with a digit. PHP is case-sensitive, so greet and Greet are different functions.

The body is the block of code between curly braces. It can contain echo, variable assignments and other statements. Names like printHeader or getUser that describe an action are a good habit.

Exercise Print a welcome message

Define a parameterless function named printWelcome. In the body, write echo "Welcome!" . "\n";. Then call the function once.

Show example solution

Define with function printWelcome() { ... }, put echo "Welcome!" . "\n"; in the body, then call with printWelcome();.
Example solution:
<?php
// Define printWelcome and call it
function printWelcome() {
    echo "Welcome!" . "\n";
}
printWelcome();

Test yourself

Which is a valid function definition?
- greet() { echo "Hi"; }
- function greet() { echo "Hi"; }
- func greet() { echo "Hi"; }
- function greet[] { echo "Hi"; }
Show answer

function greet() { echo "Hi"; } — Correct. The function keyword, name, parentheses and braces are required.

Complete the function name

function ____() {
    echo "Merhaba";
}

Show answer

function greet() {
    echo "Merhaba";
}

Match the parts of a function

function

Keyword
greet

Function name
{ echo "Hi"; }

Body

Next lesson: Calling functions

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