Blood Type / Blood Group Regex for PHP

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching blood type / blood group, 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
// Blood Type / Blood Group
// ReDoS-safe | RegexVault — Identity & PII > Biometric & Physical

define('BLOOD_TYPE_BLOOD_GROUP_PATTERN', '/^(A|B|AB|O)[+-]$/');

function validate_blood_type_blood_group(string $input): bool {
    return (bool) preg_match(BLOOD_TYPE_BLOOD_GROUP_PATTERN, $input);
}

// Example
var_dump(validate_blood_type_blood_group("A+")); // 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

ABO blood groups: A, B, AB, O. Rh factor: + (positive) or - (negative). O- (O negative) is the universal donor for red blood cells. AB+ is the universal recipient. Blood type is health data classified as sensitive under GDPR Article 9.