Ethereum Checksummed Address (EIP-55) Regex for PHP

What this pattern does

This page provides a well-structured, multi-part regular expression for matching ethereum checksummed address (eip-55), ported and verified for PHP. Financial data validation has zero tolerance for false negatives — a missed invalid entry can corrupt downstream calculations. 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
// Ethereum Checksummed Address (EIP-55)
// ReDoS-safe | RegexVault — Finance > Crypto

define('ETHEREUM_CHECKSUMMED_ADDRESS_EIP55_PATTERN', '/^0x(?:[0-9A-F]{40}|[0-9a-f]{40}|(?:[0-9a-fA-F]{40}))$/');

function validate_ethereum_checksummed_address_eip55(string $input): bool {
    return (bool) preg_match(ETHEREUM_CHECKSUMMED_ADDRESS_EIP55_PATTERN, $input);
}

// Example
var_dump(validate_ethereum_checksummed_address_eip55("0xAb8483F64d9C6d1EcF9b849Ae677dD3315835cb2")); // bool(true)

Test Cases

When to use this pattern

This pattern is drawn from the Finance > Crypto 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

EIP-55 checksum embeds a SHA3 hash of the lowercase address in the casing of the hex letters. A correctly checksummed address has mixed case. Regex alone cannot verify EIP-55 — use a library. This pattern just validates the format.