Docker Image Full Reference Regex for PHP

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching docker image full reference, 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
// Docker Image Full Reference
// ReDoS-safe | RegexVault — Dev & Systems > Docker

define('DOCKER_IMAGE_FULL_REFERENCE_PATTERN', '/^(?:(?:[a-zA-Z0-9][a-zA-Z0-9\-._]*(?::[0-9]+)?)\/)?(?:[a-z][a-z0-9\-._]*\/)?[a-z][a-z0-9\-._]*(?::([a-zA-Z0-9][a-zA-Z0-9._\-]{0,127})|@(sha256:[a-fA-F0-9]{64}))?$/');

function validate_docker_image_full_reference(string $input): bool {
    return (bool) preg_match(DOCKER_IMAGE_FULL_REFERENCE_PATTERN, $input);
}

// Example
var_dump(validate_docker_image_full_reference("nginx")); // bool(true)

Test Cases

When to use this pattern

This pattern is drawn from the Dev & Systems > Docker 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

Group 1 = tag, group 2 = digest. Docker resolves bare names like 'nginx' to 'docker.io/library/nginx:latest'. Always specify the full reference in IaC and CI/CD pipelines.