INI File Section Header Regex for PHP

What this pattern does

This page provides a well-structured, multi-part regular expression for matching ini file section header, 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
// INI File Section Header
// ReDoS-checked | RegexVault — Dev & Systems > Config

define('INI_FILE_SECTION_HEADER_PATTERN', '/^\[([a-zA-Z_][a-zA-Z0-9_.\-\s]{0,254})\]\s*(?:[;#].*)?$/');

function validate_ini_file_section_header(string $input): bool {
    return (bool) preg_match(INI_FILE_SECTION_HEADER_PATTERN, $input);
}

// Example
var_dump(validate_ini_file_section_header("[database]")); // bool(true)

Test Cases

When to use this pattern

This pattern is drawn from the Dev & Systems > Config category and has been checked for ReDoS risk. 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 = section name (may contain spaces). Inline comments with ; or # are accepted. The m flag treats ^ as start-of-line. Python configparser uses [DEFAULT] as a special fallback section.