24-Hour Time with Seconds (HH:MM:SS) Regex for PHP

What this pattern does

This page provides a well-structured, multi-part regular expression for matching 24-hour time with seconds (hh:mm:ss), 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
// 24-Hour Time with Seconds (HH:MM:SS)
// ReDoS-checked | RegexVault — Localization > Time Formats

define('24HOUR_TIME_WITH_SECONDS_HHMMSS_PATTERN', '/^(2[0-3]|[01][0-9]):([0-5][0-9]):([0-5][0-9])$/');

function validate_24hour_time_with_seconds_hhmmss(string $input): bool {
    return (bool) preg_match(24HOUR_TIME_WITH_SECONDS_HHMMSS_PATTERN, $input);
}

// Example
var_dump(validate_24hour_time_with_seconds_hhmmss("00:00:00")); // bool(true)

Test Cases

When to use this pattern

This pattern is drawn from the Localization > Time Formats 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

Requires zero-padded hours (09, not 9). Does not include fractional seconds. For sub-second precision, see loc-time-03. Note: 23:59:60 would be a leap second — technically valid in UTC but rare.