Last updated: August 27, 2026.
A PHP function packages one task behind a reusable name. Parameters supply inputs, and a declared return type makes the result easier to understand and verify.
Define and call a function
<?php
declare(strict_types=1);
function calculateTotal(float $price, int $quantity): float
{
return $price * $quantity;
}
$total = calculateTotal(19.95, 3);
echo number_format($total, 2);
?>Default and named arguments
<?php
declare(strict_types=1);
function formatPrice(float $amount, string $currency = 'USD'): string
{
return $currency . ' ' . number_format($amount, 2);
}
echo formatPrice(amount: 24.5);
?>Keep dependencies explicit
Variables declared inside a function are local to it. Pass required values as arguments instead of relying on mutable global state.
<?php
declare(strict_types=1);
function discountedPrice(float $price, float $rate): float
{
return $price * (1 - $rate);
}
echo discountedPrice(100, 0.15);
?>Use nullable and union types only when those alternatives are meaningful to callers. See user-defined functions in the PHP manual.
