How To Synchronize Your Timezones in PHP and MySQL

PHP and MySQL are separate processes with their own default timezone configurations. You’re unlikely to run into timezone issues during development or if you’re deploying a single web application to your server. In that situation, PHP and MySQL can use the server’s time settings. However, what if:

Your application can be set to the user’s timezone?
You’re running two or more applications with different timezone requirements?
Your application is installed on a shared server and you can’t set the default timezones?

Many developers solve the problem by shifting all date/time responsibility to PHP. They may also convert dates to Unix timestamp integers for simpler handling, although you should be wary of the Y2K38 Bug. While that can be a reliable solution, there are several drawbacks:

You’re creating additional work for yourself.
Your application requires additional processing to translate dates.
It not easy to directly examine dates within a table.
Some date-based SQL queries become difficult — if not impossible, e.g. return all records saved on a Monday.
You’re unable to use MySQL date/time functions such as NOW().

Fortunately, you can synchronize PHP and MySQL timezones prior to updating or querying the database. Your application will require a single configuration variable which defines PHP’s timezone, e.g.


<?php
define('TIMEZONE', 'America/New_York');

We’ll use that to set PHP’s default timezone:


date_default_timezone_set(TIMEZONE);

What about MySQL? It’s possible to set its default timezone at the start of every session — I’d recommend doing it after you’ve connected to the database. The command is:


SET time_zone='offset';

where offset is a string value representing the difference to UTC/GMT, e.g. ‘-4:00’, ‘+3:00’, ‘+10:30’, etc. Note that the +/- sign is essential — even for zero — and timezone offsets are not necessarily a whole hour. So let’s write a little PHP to parse the timezone offset and format a string MySQL can understand. First, we’ll create a new DateTime object, find the offset in seconds, and convert it to minutes:


$now = new DateTime();
$mins = $now->getOffset() / 60;

We can now calculate whole hours and minutes. The first line determines whether the offset is positive or negative, then converts the value to a positive number to make the calculation easier:


$sgn = ($mins < 0 ? -1 : 1);
$mins = abs($mins);
$hrs = floor($mins / 60);
$mins -= $hrs * 60;

PHP’s sprintf function can then be used to format the string:


$offset = sprintf('%+d:%02d', $hrs*$sgn, $mins);

Finally, we execute the SET time_zone command. The following lines provide an example, but you should use your own database library where possible:


$db = new PDO('mysql:host=localhost;dbname=test', 'dbuser', 'dbpassword');
$db->exec("SET time_zone='$offset';");

The PHP and MySQL timezones are now synchronized within your application.

tip: What’s with the backslashes?

You may have noticed the initial backslash when creating instances of the DateTime and PDO base class. These may be necessary if you’re using namespaces within your PHP application. You don’t need to remove them if you’re not.

Frequently Asked Questions (FAQs) on Synchronizing PHP and MySQL Timezone Configuration

Why is it important to synchronize PHP and MySQL timezones?

Synchronizing PHP and MySQL timezones is crucial for the accurate functioning of your application. If the timezones are not synchronized, it can lead to discrepancies in data processing and reporting. For instance, if your PHP script is running in a different timezone than your MySQL database, the time recorded in the database might not match the actual time the event occurred. This can lead to confusion and errors in data analysis and decision-making processes.

How can I set the timezone in PHP?

You can set the timezone in PHP using the date_default_timezone_set() function. This function requires a string parameter that represents the desired timezone. For example, to set the timezone to UTC, you would use the following code: date_default_timezone_set(‘UTC’);

How can I set the timezone in MySQL?

You can set the timezone in MySQL using the SET time_zone command. This command requires a string parameter that represents the desired timezone. For example, to set the timezone to UTC, you would use the following SQL command: SET time_zone=’+00:00′;

What are the common issues faced when synchronizing PHP and MySQL timezones?

Some common issues include discrepancies in time data, errors in data processing, and confusion in data analysis. These issues can occur if the PHP and MySQL timezones are not properly synchronized. It’s also important to note that daylight saving time can cause issues if not accounted for.

How can I check the current timezone in PHP?

You can check the current timezone in PHP using the date_default_timezone_get() function. This function returns a string that represents the current timezone. For example, the following code will print the current timezone: echo date_default_timezone_get();

How can I check the current timezone in MySQL?

You can check the current timezone in MySQL using the SELECT @@global.time_zone command. This command returns a string that represents the current timezone. For example, the following SQL command will return the current timezone: SELECT @@global.time_zone;

Can I set different timezones for different PHP scripts?

Yes, you can set different timezones for different PHP scripts. Each script can have its own timezone setting using the date_default_timezone_set() function. However, it’s generally recommended to keep the timezone consistent across all scripts to avoid confusion and errors.

Can I set different timezones for different MySQL databases?

Yes, you can set different timezones for different MySQL databases. Each database can have its own timezone setting using the SET time_zone command. However, it’s generally recommended to keep the timezone consistent across all databases to avoid confusion and errors.

How can I handle daylight saving time when synchronizing PHP and MySQL timezones?

Both PHP and MySQL provide support for daylight saving time. In PHP, you can use the date() function with the I (capital i) format character to check if daylight saving time is in effect. In MySQL, you can use the named timezones that automatically adjust for daylight saving time.

What are the best practices for synchronizing PHP and MySQL timezones?

Some best practices include setting the timezone at the beginning of your scripts, using the same timezone for PHP and MySQL, accounting for daylight saving time, and regularly checking and updating the timezone settings as needed. It’s also recommended to use named timezones instead of UTC offsets, as they automatically adjust for daylight saving time.