12-Hour Time (H:MM AM/PM) Regex for PHP

What this pattern does

This page provides a well-structured, multi-part regular expression for matching 12-hour time (h:mm am/pm), 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
// 12-Hour Time (H:MM AM/PM)
// ReDoS-safe | RegexVault — Localization > Time Formats

define('12HOUR_TIME_HMM_AMPM_PATTERN', '/^(1[0-2]|0?[1-9]):([0-5][0-9])(?::([0-5][0-9]))?\s?(AM|PM|am|pm|Am|Pm)$/');

function validate_12hour_time_hmm_ampm(string $input): bool {
    return (bool) preg_match(12HOUR_TIME_HMM_AMPM_PATTERN, $input);
}

// Example
var_dump(validate_12hour_time_hmm_ampm("12:30 PM")); // bool(true)

Test Cases

When to use this pattern

This pattern is drawn from the Localization > Time Formats 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

12:00 AM = midnight, 12:00 PM = noon — the most commonly confused values. 12-hour format is standard in US, UK, Australia, and parts of Asia. Many others use 24-hour exclusively.