Debian 12 - Install PHP 8.4

The easiest way to install later versions of PHP such as PHP 8.4 is to add Ondrej's repository.

sudo apt update \
  && sudo apt install ca-certificates apt-transport-https -y \
  && sudo wget -O /usr/share/keyrings/deb.sury.org-php.gpg https://packages.sury.org/php/apt.gpg \
  && sudo sh -c 'echo "deb [signed-by=/usr/share/keyrings/deb.sury.org-php.gpg] https://packages.sury.org/php/ $(lsb_release -sc) main" \
  > /etc/apt/sources.list.d/php.list'

Then you just need to install the PHP version you want. E.g.

sudo apt update \
  && sudo apt install php8.4-cli -y

Removing Existing PHP

If you had already installed PHP from native packages remove it before installing the later version:

sudo apt-get remove php8.2 php8.2-* -y
sudo apt autoremove -y