ISO 639-1 Language Code Regex for PHP

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching iso 639-1 language code, 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
// ISO 639-1 Language Code
// ReDoS-safe | RegexVault — Localization > Locale & Language

define('ISO_6391_LANGUAGE_CODE_PATTERN', '/^[a-z]{2}$/');

function validate_iso_6391_language_code(string $input): bool {
    return (bool) preg_match(ISO_6391_LANGUAGE_CODE_PATTERN, $input);
}

// Example
var_dump(validate_iso_6391_language_code("en")); // bool(true)

Test Cases

When to use this pattern

This pattern is drawn from the Localization > Locale & Language 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

ISO 639-1 codes are always lowercase 2 letters. Examples: en=English, zh=Chinese, es=Spanish, ar=Arabic, hi=Hindi, ja=Japanese, ko=Korean. Not all languages have ISO 639-1 codes — use ISO 639-3 (3-char) for less common languages.