What3Words Address Regex for PHP

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching what3words address, ported and verified for PHP. Identity and credential patterns need both correctness and safety, since they're frequent targets for adversarial input. 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
// What3Words Address
// ReDoS-safe | RegexVault — Identity & PII > Location PII

define('WHAT3WORDS_ADDRESS_PATTERN', '/^[a-z]+(?:\.[a-z]+){2}$/');

function validate_what3words_address(string $input): bool {
    return (bool) preg_match(WHAT3WORDS_ADDRESS_PATTERN, $input);
}

// Example
var_dump(validate_what3words_address("filled.count.soap")); // bool(true)

Test Cases

When to use this pattern

This pattern is drawn from the Identity & PII > Location PII 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

What3Words divides the world into 3m × 3m squares, each with a unique 3-word address. The API is proprietary. Format validation can check the 3-word pattern but validity of the address requires the W3W API. 57 trillion unique combinations globally.