Australian Postcode Regex for PHP

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching australian postcode, ported and verified for PHP. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your PHP project — whether you're validating in a Laravel validator, a WordPress plugin, or a standalone PHP script.

Php Implementation

<?php
// Australian Postcode
// ReDoS-safe | RegexVault — Localization > Postal Codes

define('AUSTRALIAN_POSTCODE_PATTERN', '/^([0-9]{4})$/');

function validate_australian_postcode(string $input): bool {
    return (bool) preg_match(AUSTRALIAN_POSTCODE_PATTERN, $input);
}

// Example
var_dump(validate_australian_postcode("2000")); // bool(true)

Test Cases

When to use this pattern

This pattern is drawn from the Localization > Postal Codes category and carries a ReDoS-safe certification. That matters for PHP developers because especially relevant in PHP where PCRE backtracking limits can trigger silent failures on malicious input. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

Australian postcode ranges by state: NSW/ACT 2000-2999, VIC 3000-3999, QLD 4000-4999, SA 5000-5999, WA 6000-6999, TAS 7000-7999, NT 0800-0999. Leading zeros (NT/ACT) require string storage.