PEM Certificate Block Regex for PHP

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching pem certificate block, 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
// PEM Certificate Block
// ReDoS-safe | RegexVault — Security > Certificates & PKI

define('PEM_CERTIFICATE_BLOCK_PATTERN', '/-----BEGIN CERTIFICATE-----[\r\n]+(?:[A-Za-z0-9+\/=\r\n]{1,80}[\r\n]+)*-----END CERTIFICATE-----/');

function validate_pem_certificate_block(string $input): bool {
    return (bool) preg_match(PEM_CERTIFICATE_BLOCK_PATTERN, $input);
}

// Example
var_dump(validate_pem_certificate_block("-----BEGIN CERTIFICATE-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA
-----END CERTIFICATE-----")); // bool(true)

Test Cases

When to use this pattern

This pattern is drawn from the Security > Certificates & PKI 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

PEM format: base64-encoded DER certificate wrapped in BEGIN/END markers. Lines are max 76 characters in the standard. Use for detecting certificates in config files, code, or traffic. Parse with a proper X.509 library to extract subject, issuer, validity, and SANs.