Email Address (RFC 5321 Practical) Regex for PHP

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching email address (rfc 5321 practical), 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
// Email Address (RFC 5321 Practical)
// ReDoS-safe | RegexVault — Identity & PII > Email Address

define('EMAIL_ADDRESS_RFC_5321_PRACTICAL_PATTERN', '/^[a-zA-Z0-9.!#$%&\'*+\/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*\.[a-zA-Z]{2,}$/');

function validate_email_address_rfc_5321_practical(string $input): bool {
    return (bool) preg_match(EMAIL_ADDRESS_RFC_5321_PRACTICAL_PATTERN, $input);
}

// Example
var_dump(validate_email_address_rfc_5321_practical("user@example.com")); // bool(true)

Test Cases

When to use this pattern

This pattern is drawn from the Identity & PII > Email Address 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

Deliberately excludes quoted strings and IP address literals (RFC 5321 allows them but they are vanishingly rare in practice). The TLD must be at least 2 letters. Internationalized domain names (IDN) require Punycode encoding first.