OAuth 2.0 Refresh Token (Generic) Regex for PHP

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching oauth 2.0 refresh token (generic), 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
// OAuth 2.0 Refresh Token (Generic)
// ReDoS-safe | RegexVault — Security > OAuth & OIDC

define('OAUTH_20_REFRESH_TOKEN_GENERIC_PATTERN', '/^[A-Za-z0-9\-_.+\/=]{40,512}$/');

function validate_oauth_20_refresh_token_generic(string $input): bool {
    return (bool) preg_match(OAUTH_20_REFRESH_TOKEN_GENERIC_PATTERN, $input);
}

// Example
var_dump(validate_oauth_20_refresh_token_generic("1//0gBcDeFgHiJkLmNoPqRsTuVwXyZ01234567890aBcDeFgHiJkLmNoPqR")); // bool(true)

Test Cases

When to use this pattern

This pattern is drawn from the Security > OAuth & OIDC 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

Refresh tokens are long-lived (hours to years) credentials used to obtain new access tokens. They must be stored securely (not in localStorage or cookies without Secure/HttpOnly flags). Rotation on use (refresh token rotation) is best practice.