Dockerfile FROM Instruction Regex for PHP

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching dockerfile from instruction, 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
// Dockerfile FROM Instruction
// ReDoS-safe | RegexVault — Dev & Systems > Docker

define('DOCKERFILE_FROM_INSTRUCTION_PATTERN', '/^FROM\s+(?:--platform=[^\s]+\s+)?([a-z][a-z0-9\-._\/]*(?::[a-zA-Z0-9._\-]+|@sha256:[a-fA-F0-9]{64})?)(?:\s+AS\s+([a-zA-Z][a-zA-Z0-9_\-]*))?$/');

function validate_dockerfile_from_instruction(string $input): bool {
    return (bool) preg_match(DOCKERFILE_FROM_INSTRUCTION_PATTERN, $input);
}

// Example
var_dump(validate_dockerfile_from_instruction("FROM 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 = image reference, group 2 = AS alias. Multi-stage builds use FROM...AS extensively. 'scratch' is a special minimal base image. --platform enables cross-platform builds.