PHP 8.3 is released with typed class constants, a json_validate function, and more

The PHP team has released PHP 8.3 today with typed class constants, a json_validate() function, dynamically fetching a class constant, the #[Override] attribute, and more:

• Typed Class Constants
• json_validate() function
• Dynamic class constant fetch
• Marking overridden methods
• mb_str_pad() function
• Fallback value syntax for INI ENV variables
• Support linting multiple files at once
• More Appropriate Date/Time Exceptions
• Deep-cloning of readonly properties
• Randomizer Additions
• and more...

#Typed Class Constants

In PHP 8.2, it was still not possible to declare constant (const) types, which can lead to confusion or implications about the type you're working with:

interface I {
    const TEST = "Test";  // We may naively assume that the TEST constant is always a string
}
 
class Foo implements I {
    const TEST = [];      // But it may be an array...
}
 
class Bar extends Foo {
    const TEST = null;    // Or null
}

Here's an example of how typed constants look in PHP 8.3:

interface I {
    const string TEST = E::TEST;   // I::TEST is a string as well
}
 
class Foo implements I {
    use T;
 
    const string TEST = E::TEST;  // Foo::TEST must also be a string
}
 
class Bar extends Foo {
    const string TEST = "Test2";  // Bar::TEST must also be a string, but the value can change
}
 
// Error example
 
// Fatal error: Cannot use array as value for class constant
// Foo::PHP of type string
class Buzz implements I {
    const string PHP = [];
}

#The json_validate() function

To validate JSON in PHP, you would need to either configure the JSON_THROW_ON_ERROR flag, use json_last_error, or even just check for null on a json_decode() call:

json_decode(json: '{"foo": "bar}', flags: JSON_THROW_ON_ERROR);
 
// JsonException  Control character error, possibly incorrectly encoded.

As of PHP 8.3, you can also validate JSON using the json_validate() function:

// Valid
json_validate('{"framework": "Laravel"}'); // true
 
// Invalid
json_validate('{"framework": "Laravel}'); // false
 
json_last_error_msg(); // Control character error, possibly incorrectly encoded
json_last_error(); // 3

#Dynamic class constant fetch

In PHP >= 8.2, dynamically fetching a class constant value was only possible using the constant() function. The following would result in a syntax error:

class Framework {
    const NAME = 'Laravel';
}
 
$name = 'NAME';
 
// You could achieve this with the constant() function
constant(Framework::class . '::' . $name); // Laravel
 
// This following is a syntax error in >=v8.2.0
echo Framework::{$name};
// ParseError  syntax error, unexpected token ";", expecting "(".

As of PHP 8.3, you can now access constants dynamically from a class,

class Framework {
    const NAME = 'Laravel';
}
 
$name = 'NAME';
 
// Syntax error in <= v8.2.0
echo Framework::{$name}; // Laravel

#Fallback value for environment variables in INI files

One of my favorite additions to PHP 8.3 is providing a default value when using environment variables to define INI settings. This will simplify Docker defaults without having to specify the defaults as ENV blocks in a Dockerfile. I am sure there are plenty of use cases out there that will be simplified by this.

Let's say, for example, that you want to allow a DRUPAL_FPM_PORT ENV value to configure an INI value for the www FPM pool:

error_log = syslog
daemonize = false
 
[www]
listen = localhost:${DRUPAL_FPM_PORT}

The DRUPAL_FPM_PORT must be defined, and no default was possible! Now, you can do the following, which should feel familiar to a bash/shell script:

[www]
listen = localhost:${DRUPAL_FPM_PORT:-9000}

Imagine shipping an xdebug.ini file as part of your Dockerfile for development with sensible defaults yet allowing developers to override values they see fit.

#Randomizer Additions

PHP 8.3 includes Randomizer Additions, including a new getBytesFromString() method, which is convenient to get random bytes from a source string:

$randomizer = new \Random\Randomizer();
 
printf(
    "%s.example.com",
    $randomizer->getBytesFromString('abcdefghijklmnopqrstuvwxyz0123456789', 16)
);
 
// 3zsw04eiubcf82jd.example.com
 
 
// Generate a random code for multi-factor authentication
$randomizer = new \Random\Randomizer(new \Random\Engine\Secure());
 
echo implode('-', str_split($randomizer->getBytesFromString('0123456789', 20), 5));
 
// 11551-80418-27047-42075

#Learn more

To get up to speed on these new features, check out the PHP 8.3.0 Release Announcement page for examples before/after PHP 8.3. Be sure to check out the deprecations and backward compatibility breaks.