Gender Marker (Medical / Governmental) Regex for PHP

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching gender marker (medical / governmental), 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
// Gender Marker (Medical / Governmental)
// ReDoS-safe | RegexVault — Identity & PII > Biometric & Physical

define('GENDER_MARKER_MEDICAL_GOVERNMENTAL_PATTERN', '/^(?:M|F|X|O|U|N|NB|MALE|FEMALE|NON-BINARY|UNKNOWN|UNSPECIFIED|PREFER_NOT_TO_SAY|INTERSEX)$/');

function validate_gender_marker_medical_governmental(string $input): bool {
    return (bool) preg_match(GENDER_MARKER_MEDICAL_GOVERNMENTAL_PATTERN, $input);
}

// Example
var_dump(validate_gender_marker_medical_governmental("M")); // bool(true)

Test Cases

When to use this pattern

This pattern is drawn from the Identity & PII > Biometric & Physical 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

ICAO uses M/F/X for passports. HL7 FHIR uses M/F/O/U/N codes. Government documents vary: AU allows X (non-binary), UK driving licence adds a 5-month offset for female, CA federal documents allow X. The X gender marker is now recognized in many jurisdictions.