PHP Tutorial · Functions and Arrays · Lesson 17 of 38

PHP Functions

Define functions with typed parameters, defaults, named arguments and return types.

Defining functions

Example 1Try it yourself

<?php
function greet(string $name): string
{
    return "Hello, $name!";
}
echo greet("Ada"), "\n";

Output

Hello, Ada!

Type declarations

Declare parameter and return types. With declare(strict_types=1); PHP rejects wrong types instead of converting them. Types include int, float, string, bool, array, class names, nullable ?string, unions int|float, and void.

Defaults and named arguments

Parameters can have default values. PHP 8 named arguments let you pass arguments by name, in any order, skipping optional ones:

Example 2Try it yourself

<?php
function makeTag(string $text, string $tag = "p", ?string $class = null): string
{
    $attr = $class ? " class=\"$class\"" : "";
    return "<$tag$attr>$text</$tag>";
}
echo makeTag("Hi"), "\n";
echo makeTag("Title", "h1"), "\n";
echo makeTag("Note", class: "muted"), "\n";

Output

<p>Hi</p>
<h1>Title</h1>
<p class="muted">Note</p>

Variadic functions

...$numbers collects any number of arguments into an array; ...$array spreads an array into arguments:

Example 3Try it yourself

<?php
function total(float ...$amounts): float
{
    return array_sum($amounts);
}
echo total(1.5, 2.5, 3), "\n";
$cart = [10, 20, 5];
echo total(...$cart), "\n";

Output

7
35

Anonymous and arrow functions

Closures can be stored in variables and passed to functions like array_map(). Arrow functions (fn) capture outer variables automatically; classic closures need use:

Example 4Try it yourself

<?php
$rate = 1.2;
$withTax = fn(float $p): float => $p * $rate;
$discount = function (float $p) use ($rate): float {
    return $p / $rate;
};
print_r(array_map($withTax, [10, 20]));
echo $discount(120), "\n";

Output

Array
(
    [0] => 12
    [1] => 24
)
100

Test yourself

Which PHP 8 feature lets you call makeTag('Hi', class: 'x')?

Default parameters
Named arguments
Variadic functions
Closures

Show answer

Answer: Named arguments