PHP Version

7.3 or higher. You can always check the composer.json file to figure that out https://github.com/laravel/laravel/blob/8.x/composer.json#L11

You can always refer to docs Laravel 8 Server Requirements

Server Requirements

The Laravel framework has a few system requirements. You should ensure that your web server has the following minimum PHP version and extensions:

• PHP >= 7.3
• BCMath PHP Extension
• Ctype PHP Extension
• Fileinfo PHP Extension
• JSON PHP Extension
• Mbstring PHP Extension
• OpenSSL PHP Extension
• PDO PHP Extension
• Tokenizer PHP Extension
• XML PHP Extension