Debian Squeeze (6.0) is a legacy system that shipped with PHP 5.3.3 by default. Since this version reached end-of-life in 2014, upgrading is crucial for security and compatibility. The main obstacles are:

• Official Debian repositories no longer support Squeeze
• Package dependencies can break during manual upgrades
• PHP 5.3.3 lacks modern features like namespace support

Before upgrading, take these precautions:

# Create backup of PHP configuration
sudo cp -R /etc/php5 /etc/php5_backup

# Backup web server config
sudo cp /etc/apache2/apache2.conf /etc/apache2/apache2.conf.bak

# List currently installed PHP modules
dpkg -l | grep php

The most reliable approach for Debian Squeeze is using Dotdeb:

# Add Dotdeb repository
echo "deb http://packages.dotdeb.org squeeze all" | sudo tee -a /etc/apt/sources.list
echo "deb-src http://packages.dotdeb.org squeeze all" | sudo tee -a /etc/apt/sources.list

# Add GPG key
wget https://www.dotdeb.org/dotdeb.gpg
sudo apt-key add dotdeb.gpg

# Update and upgrade
sudo apt-get update
sudo apt-get install php5 php5-cli php5-common

For complete version control:

# Install dependencies
sudo apt-get install build-essential libxml2-dev libcurl4-openssl-dev \
libjpeg-dev libpng-dev libmcrypt-dev libssl-dev

# Download PHP source (example: PHP 5.6)
wget https://www.php.net/distributions/php-5.6.40.tar.gz
tar -xvzf php-5.6.40.tar.gz
cd php-5.6.40

# Configure and compile
./configure --prefix=/usr/local/php5.6 \
--with-config-file-path=/etc/php5.6 \
--with-mysql \
--with-mysqli \
--with-apxs2=/usr/bin/apxs2

make
sudo make install

For phpMyAdmin upgrades:

# Remove old version
sudo apt-get remove phpmyadmin

# Download latest
wget https://files.phpmyadmin.net/phpMyAdmin/5.1.1/phpMyAdmin-5.1.1-all-languages.tar.gz
tar -xvzf phpMyAdmin-5.1.1-all-languages.tar.gz
sudo mv phpMyAdmin-5.1.1-all-languages /usr/share/phpmyadmin

# Create config directory
sudo mkdir /etc/phpmyadmin
sudo cp /usr/share/phpmyadmin/config.sample.inc.php /usr/share/phpmyadmin/config.inc.php

After upgrading, verify everything works:

# Check PHP version
php -v

# Test Apache configuration
sudo apache2ctl configtest

# Restart services
sudo service apache2 restart

Debian Squeeze (6.0) is an old stable release that reached end-of-life in 2016. The default repositories no longer receive updates, making PHP 5.3.3 the last officially supported version. However, with some repository adjustments, we can upgrade to newer PHP versions.

The most reliable way to upgrade PHP on Squeeze is using Dotdeb repositories. First, backup your current PHP configuration:

sudo cp -R /etc/php5 /etc/php5_backup
sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak

Now add Dotdeb to your sources.list:

echo "deb http://packages.dotdeb.org squeeze all" | sudo tee -a /etc/apt/sources.list
echo "deb-src http://packages.dotdeb.org squeeze all" | sudo tee -a /etc/apt/sources.list
echo "deb http://packages.dotdeb.org squeeze-php56 all" | sudo tee -a /etc/apt/sources.list
echo "deb-src http://packages.dotdeb.org squeeze-php56 all" | sudo tee -a /etc/apt/sources.list

Import the Dotdeb GPG key and update your package lists:

wget https://www.dotdeb.org/dotdeb.gpg
sudo apt-key add dotdeb.gpg
sudo apt-get update

You can now upgrade to PHP 5.6 (the highest version supported on Squeeze via Dotdeb):

sudo apt-get install php5 php5-cli php5-fpm php5-mysql

Verify the upgrade:

php -v

For phpMyAdmin, first remove the old version:

sudo apt-get remove phpmyadmin

Then install the latest version manually:

wget https://www.phpmyadmin.net/downloads/phpMyAdmin-latest-all-languages.tar.gz
tar -xvzf phpMyAdmin-latest-all-languages.tar.gz
sudo mv phpMyAdmin-*-all-languages /usr/share/phpmyadmin

If Dotdeb doesn't work for your setup, you can try the official backports:

echo "deb http://archive.debian.org/debian squeeze-backports main" | sudo tee -a /etc/apt/sources.list
sudo apt-get update
sudo apt-get -t squeeze-backports install php5

Remember that both PHP 5.3 and 5.6 are EOL and no longer receive security updates. For production environments, consider upgrading to a newer Debian release or using containers with updated PHP versions.