IPv4 Address (as PII identifier) Regex for PHP

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching ipv4 address (as pii identifier), 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
// IPv4 Address (as PII identifier)
// ReDoS-safe | RegexVault — Identity & PII > Digital Identity

define('IPV4_ADDRESS_AS_PII_IDENTIFIER_PATTERN', '/^(?:(?:25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9][0-9]|[0-9])\.){3}(?:25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9][0-9]|[0-9])$/');

function validate_ipv4_address_as_pii_identifier(string $input): bool {
    return (bool) preg_match(IPV4_ADDRESS_AS_PII_IDENTIFIER_PATTERN, $input);
}

// Example
var_dump(validate_ipv4_address_as_pii_identifier("192.168.1.1")); // bool(true)

Test Cases

When to use this pattern

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

Under GDPR (C-582/14, Breyer v Germany), IP addresses can constitute personal data when the controller has the legal means to identify the individual. Dynamic IPs assigned by ISPs are personal data. Log files containing IP addresses must comply with GDPR retention requirements.