A PHP variadic parameter can collect unknown named arguments, but their names are preserved as string keys. Use named arguments when the keys carry meaning; use positional arguments when the function expects a simple ordered list.
Last updated: October 26, 2026.
<?php
function configure(string $service, string ...$options): array
{
return ['service' => $service, 'options' => $options];
}
$named = configure(
service: 'mailer',
transport: 'smtp',
encryption: 'tls'
);
// options: ['transport' => 'smtp', 'encryption' => 'tls']
$positional = configure('mailer', 'smtp', 'tls');
// options: [0 => 'smtp', 1 => 'tls']Both calls satisfy the string ...$options declaration. The difference is the shape of the captured array: unknown named arguments keep their names, while positional arguments receive numeric keys.
Do not repeat the variadic parameter name
The PHP function-arguments documentation explains both variable-length argument lists and named arguments. A call such as configure(options: "smtp") creates one entry whose key is options. The parameter name is not a container that can be specified repeatedly, so passing options: twice causes a duplicate named-parameter error.
PHP also forbids an ordinary positional argument after a named argument. If you need an ordered list, put every positional value first. If you need a keyed option map, give each extra argument its own meaningful name as in the example.
Unpack arrays with the intended key type
The named-arguments specification states that string-keyed values supplied through argument unpacking are treated as named arguments, while integer-keyed values are positional. Therefore configure(...["service" => "mailer", "transport" => "smtp"]) preserves the option name. A list such as ["mailer", "smtp"] remains positional.
Parameter names become part of the callable interface when callers use them, so renaming a public parameter can break consumers. Prefer a single explicit array parameter for a large or evolving configuration schema, especially when validation, defaults, or nested options are required. Continue with PHP function parameters and return types, explicit nullable parameters, and safe array traversal.
