PHP 8.5 Introduces PHP_BUILD_DATE: Know Exactly When Your PHP Was Built

Have you ever wondered when your PHP binary was actually built? In the past, finding this out meant digging through phpinfo() output or running shell commands. But with PHP 8.5, there’s finally a simple, native solution: the new predefined constant PHP_BUILD_DATE.

In this post, we’ll explore what this new constant does, why it matters, and how you can use it in your applications for debugging, logging, or pure curiosity.

🚀 What Is PHP_BUILD_DATE?

In PHP 8.5, a new global constant PHP_BUILD_DATE was introduced to give you the exact date and time your PHP binary was compiled. Here's what the constant returns:

echo PHP_BUILD_DATE;

The output might look like this:

Nov 22 2025 00:00:10

It’s a simple string showing the date and time when your PHP build was created—no need for phpinfo() or CLI tricks anymore.

This feature was actually first requested way back in 2007 in PHP Bug #41417, and it finally made it into the core after years of developer demand. 🎉

🛠️ Basic Usage: One-Liner Magic

Using the constant is as simple as it gets:

<?php
echo 'PHP Build Date: ' . PHP_BUILD_DATE;

Sample Output

PHP Build Date: Nov 22 2025 00:00:10

This is super helpful for:

• Debugging across different environments
• Verifying deployed binaries
• Checking custom-compiled PHP versions

🧮 Parsing the Build Date

Need to do more with the date? You can easily parse the string into a Unix timestamp using PHP’s strtotime() function:

<?php
$timestamp = strtotime(PHP_BUILD_DATE);
echo 'Built at Unix timestamp: ' . $timestamp;

This is useful when comparing the build date to other events or generating logs.

📅 Formatting with DateTimeImmutable

Want more control over the date format or timezone? Create a DateTimeImmutable object from the constant:

<?php
$buildDate = new DateTimeImmutable(PHP_BUILD_DATE);
echo 'Build Year: ' . $buildDate->format('Y');

You can now format it any way you like:

• Y – Year (e.g., 2025)
• F – Full month name (e.g., November)
• c – ISO-8601 format
• And much more!

Need it in UTC? Just set the timezone:

$utcDate = $buildDate->setTimezone(new DateTimeZone('UTC'));
echo 'UTC Time: ' . $utcDate->format('Y-m-d H:i:s');

📝 Logging the Build Date

Including the build date in your logs can be a game-changer, especially when debugging across different servers or Docker images.

Basic Example

error_log('App started — PHP build date: ' . PHP_BUILD_DATE);

With PSR-3 Logger

$logger->info('Application booted', [
    'php_build_date' => PHP_BUILD_DATE,
]);

With this, you’ll always know exactly which binary version your application was running when logs were generated.

🧩 Pro Tips & Gotchas

Here are a few things to keep in mind:

🕒 Format Caveat

The constant outputs in the format M j Y H:i:s, like Nov 22 2025 00:00:10. This is not ISO-8601, so you’ll usually want to parse it into a DateTimeImmutable or use strtotime().

🌍 Timezone Note

The timestamp reflects the build environment’s timezone, which might differ from your runtime or system timezone. Convert as needed.

🔙 Backward Compatibility

Older PHP versions (< 8.5) won’t recognize this constant. To avoid errors:

if (defined('PHP_BUILD_DATE')) {
    echo PHP_BUILD_DATE;
} else {
    echo 'Not supported in this PHP version.';
}

🧾 Conclusion

The introduction of PHP_BUILD_DATE in PHP 8.5 might seem like a small addition, but it fills a long-standing gap in the PHP ecosystem. Whether you’re deploying applications, troubleshooting environments, or simply curious about your server setup, this constant brings clarity with zero hassle.

So go ahead—drop a PHP_BUILD_DATE in your logs, your debug tools, or even a fun Easter egg on your “About” page.

Happy coding! 🐘