Linux: Switch Between Multiple PHP Versions

This guide shows you how to switch between multiple PHP versions on Ubuntu Linux systems using Apache web server.

Overview

When working on different projects that require different PHP versions, you need the ability to switch between PHP versions easily. This guide covers:

  • Manual switching between specific PHP versions

  • Automated switching using a shell script

  • Managing PHP versions for Apache and CLI

Reference: https://ostechnix.com/how-to-switch-between-multiple-php-versions-in-ubuntu/

Prerequisites

Before switching PHP versions, ensure you have:

  • Multiple PHP versions installed on your system

  • Apache web server installed

  • Root or sudo access

Manual PHP Version Switching

Switch From PHP 7.4 to PHP 8.1

Follow these steps to switch from PHP 7.4 to PHP 8.1:

  1. Disable the current PHP version (7.4) for Apache:

    sudo a2dismod php7.4

  2. Enable the target PHP version (8.1) for Apache:

    sudo a2enmod php8.1

  3. Set PHP 8.1 as the default CLI version:

    sudo update-alternatives --set php /usr/bin/php8.1

  4. Verify the installed PHP versions (optional):

    sudo update-alternatives --config php

    This command shows all installed PHP versions and allows you to select the default.

  5. Restart Apache to apply changes:

    sudo systemctl restart apache2

  6. Verify the switch:

    php -v

    This should show PHP 8.1 as the active version.

Switch From PHP 8.1 to PHP 7.4

To switch back from PHP 8.1 to PHP 7.4, follow these steps:

  1. Disable PHP 8.1 for Apache:

    sudo a2dismod php8.1

  2. Enable PHP 7.4 for Apache:

    sudo a2enmod php7.4

  3. Set PHP 7.4 as the default CLI version:

    sudo update-alternatives --set php /usr/bin/php7.4

  4. Verify the installed PHP versions (optional):

    sudo update-alternatives --config php

  5. Restart Apache to apply changes:

    sudo systemctl restart apache2

  6. Verify the switch:

    php -v

    This should now show PHP 7.4 as the active version.

Troubleshooting

Error: Module does not exist

If you encounter an error like ERROR: Module php8.1 does not exist!, it means the Apache PHP module is not installed. Install it with:

sudo apt-get install libapache2-mod-php8.1

Replace php8.1 with the version you need (e.g., php7.4, php8.0, php8.2, php8.3, php8.4).

Switch PHP Script

For frequent PHP version switching, you can use an automated shell script that simplifies the process with a single command.

See also

For detailed installation instructions and the complete script, see Script 6: Automated PHP Version Switching

The automated script allows you to:

  • Switch PHP versions with a single command (e.g., switch 8.1)

  • Automatically update both Apache and CLI PHP versions

  • Disable all other PHP versions for clean switching

  • Restart Apache automatically after switching

  • Support multiple PHP versions (5.6, 7.0, 7.1, 7.2, 7.3, 7.4, 8.0, 8.1, 8.2, 8.3, 8.4)

Quick Example

After installing the script from the bash service scripts guide:

# Switch to PHP 8.1
switch 8.1

# Switch to PHP 7.4
switch 7.4

# View help
switch --help

Script Output

When you run the switch command, you’ll see output similar to this:

PHP version switch output

Fig. 38 PHP version switch command output

Best Practices

Version Management

  • Test before production: Always test version switches in development environments first

  • Check compatibility: Ensure your application supports the target PHP version

  • Document requirements: Keep track of which projects require which PHP versions

  • Use version control: Include PHP version requirements in your project documentation

Common Use Cases

Scenario 1: Different Projects

If you have Project A requiring PHP 7.4 and Project B requiring PHP 8.1, switch versions as needed:

# Working on Project A
switch 7.4

# Working on Project B
switch 8.1
Scenario 2: Testing Upgrades

When upgrading applications, test with newer PHP versions:

# Current version
switch 7.4
# Run tests

# Test with new version
switch 8.1
# Run tests again
Scenario 3: Debugging

Switch to specific versions to reproduce or debug issues:

switch 8.0  # If issue reported on PHP 8.0

Additional Commands

Check Current PHP Version

# CLI version
php -v

# Apache version (via phpinfo)
# Create a file: /var/www/html/info.php with content: <?php phpinfo(); ?>
# Then access: http://localhost/info.php

List Installed PHP Versions

# List all installed PHP packages
dpkg -l | grep php | grep -v php-common

Install Additional PHP Versions

# Add PHP repository (if not already added)
sudo add-apt-repository ppa:ondrej/php
sudo apt update

# Install specific PHP version
sudo apt install php8.2 php8.2-cli php8.2-common libapache2-mod-php8.2

Tip

Always keep your PHP installations updated with security patches. Use sudo apt update && sudo apt upgrade regularly.