SHA-256 Hash Regex for PHP

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching sha-256 hash, ported and verified for PHP. In security-sensitive code, using an unverified regex can open the door to both false positives and denial-of-service attacks. 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
// SHA-256 Hash
// ReDoS-safe | RegexVault — Security > Password Formats

define('SHA256_HASH_PATTERN', '/^[a-f0-9]{64}$/');

function validate_sha256_hash(string $input): bool {
    return (bool) preg_match(SHA256_HASH_PATTERN, $input);
}

// Example
var_dump(validate_sha256_hash("e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855")); // bool(true)

Test Cases

When to use this pattern

This pattern is drawn from the Security > Password Formats 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

SHA-256 is part of the SHA-2 family, still cryptographically secure. Used for certificates, code signing, TLS, and file integrity. For password hashing, always use SHA-256 within a proper password hashing function (PBKDF2, Argon2) — raw SHA-256 alone is not suitable for passwords.