Kubernetes Label / Annotation Value Regex for PHP

What this pattern does

This page provides a well-structured, multi-part regular expression for matching kubernetes label / annotation value, ported and verified for PHP. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. 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
// Kubernetes Label / Annotation Value
// ReDoS-safe | RegexVault — Dev & Systems > Config

define('KUBERNETES_LABEL_ANNOTATION_VALUE_PATTERN', '/^[a-zA-Z0-9](?:[a-zA-Z0-9_.\-]{0,61}[a-zA-Z0-9])?$|^$/');

function validate_kubernetes_label_annotation_value(string $input): bool {
    return (bool) preg_match(KUBERNETES_LABEL_ANNOTATION_VALUE_PATTERN, $input);
}

// Example
var_dump(validate_kubernetes_label_annotation_value("production")); // bool(true)

Test Cases

When to use this pattern

This pattern is drawn from the Dev & Systems > Config 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

Label values can be empty (for boolean-style presence checks). Must begin and end with alphanumeric if non-empty. Max 63 chars. Label keys have a separate format (optional prefix/name with different rules).