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Functions

Typed parameters and return types, defaults, named arguments, arrow functions and closures.

Runs in Zerethon IDE · PHP 8.4 Official PHP documentation ↗
main.php 
<?php

declare(strict_types=1);

function greet(string $name, string $greeting = 'Hello'): string
{
    return "$greeting, $name!";
}

function stats(int ...$numbers): array
{
    return [min($numbers), max($numbers), array_sum($numbers) / count($numbers)];
}

echo greet('Ada'), ' ', greet(greeting: 'Hi', name: 'Linus'), "\n";
[$low, $high, $mean] = stats(4, 8, 6);
echo "$low $high $mean\n";

$factor = 3;
$times = fn (int $x): int => $x * $factor;      // captures $factor automatically
$add = function (int $x) use ($factor): int {   // a closure lists what it uses
    return $x + $factor;
};
echo $times(5), ' ', $add(5), "\n";

Output

Hello, Ada! Hi, Linus!
4 8 6
15 8
  • Functions do not see outside variables: pass them as parameters, or use ($x) in a closure.
  • Arrow functions (fn) are one expression and capture outside variables by value.
  • Types are checked when the function is called; with strict_types=1, greet(5) is a TypeError instead of a conversion.

Related topics

Official references