Named Arguments in Built-in PHP Functions

Also Known As

TL;DR

Explanation

Named arguments (PHP 8.0) apply to built-in functions as well as userland code. This is particularly valuable for functions with many positional parameters where intermediate defaults must be skipped: array_slice($array, offset: 2, preserve_keys: true) is far clearer than array_slice($array, 2, null, true). Common built-in targets: str_contains, implode, array_map, array_filter (with mode:), htmlspecialchars (flags:, encoding:), json_encode (flags:, depth:). Caution: built-in parameter names are part of PHP's public API from 8.0 onward but some names changed between versions — check the manual. Named arguments cannot be used with variadic functions that spread into ...$args.

Common Misconception

Why It Matters

Common Mistakes

• Not using named arguments for built-in functions with confusing parameter order — str_contains vs strpos argument order differs.
• Renaming function parameters in your own API and forgetting it is a breaking change for named argument callers.
• Using named arguments with variadic functions — they interact in non-obvious ways.
• Not using named arguments for clarity in calls with boolean flags: htmlspecialchars($str, double_encode: false).

Code Examples

// Confusing positional arguments:
$result = array_slice($arr, 1, 5, true); // What is 'true'?
$encoded = htmlspecialchars($str, ENT_QUOTES | ENT_HTML5, 'UTF-8', false); // Last arg?

// Named — self-documenting:
$result = array_slice($arr, offset: 1, length: 5, preserve_keys: true);
$encoded = htmlspecialchars($str, double_encode: false);

// Skip intermediate positional arguments cleanly
$slice = array_slice($items, offset: 5, preserve_keys: true);
$encoded = json_encode($data, flags: JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE);

References

• ↗ https://www.php.net/manual/en/functions.named-arguments.php

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