How to upgrade PHP5.6 to PHP7.4 to avoid compatibility issues?

How to upgrade PHP5.6 to PHP7.4 to avoid compatibility issues?

Overview:
As time goes by, new versions of PHP are constantly launched, and the latest version is PHP7.4. Upgrading to PHP7.4 can bring better performance, more features and better security. However, since there are some incompatible changes between PHP7.4 and previous versions, there are some issues that need to be paid attention to during the upgrade process. This article will introduce how to safely upgrade PHP5.6 to PHP7.4 and solve possible compatibility issues.

Check system requirements:
Before starting the upgrade, you must ensure that the server meets the system requirements for PHP7.4. Please perform the following operations:

1. Check the operating system version: The operating system versions supported by PHP7.4 include Ubuntu 16.04, 18.04, 20.04, Debian 9, 10, CentOS 7, 8, etc. Please make sure your operating system meets the requirements.
2. Check the system architecture: PHP7.4 supports 32-bit and 64-bit architectures. Please make sure your system architecture and PHP version match.

Backup work:
Be sure to back up your code and database before performing any upgrade operations. This is very important to protect your data and applications from unexpected loss.

Upgrade Steps:
Next, we will learn step by step how to upgrade PHP5.6 to PHP7.4:

1. Update system packages:
   Before starting the upgrade , first make sure you have the latest system packages installed. Update the package using the following command:

sudo apt-get update
sudo apt-get upgrade

2. Remove the old version of PHP:
   Before installing the new version, you need to remove the old version of PHP. Execute the following command to uninstall PHP:

sudo apt-get purge php5

3. Add PHP7.4 related warehouse:
   To install PHP7.4, you need to add the relevant warehouse to the system. Depending on the operating system you are using, execute the following commands:

Ubuntu 16.04/18.04/20.04:

sudo apt-get install software-properties-common
sudo add-apt-repository ppa:ondrej/php
sudo apt-get update

Debian 9/10:

sudo apt-get install apt-transport-https lsb-release ca-certificates
sudo wget -O /etc/apt/trusted.gpg.d/php.gpg https://packages.sury.org/php/apt.gpg
echo "deb https://packages.sury.org/php/ $(lsb_release -sc) main" | sudo tee /etc/apt/sources.list.d/php.list
sudo apt-get update

CentOS 7/8 ：

sudo yum install epel-release
sudo yum install http://rpms.remirepo.net/enterprise/remi-release-7.rpm
sudo yum install yum-utils
sudo yum-config-manager --enable remi-php74
sudo yum update

4. Install PHP7.4 and related modules:
   Execute the following command to install PHP7.4 and its related modules:

sudo apt-get install php7.4
sudo apt-get install php7.4-cli php7.4-fpm php7.4-mysql php7.4-curl php7.4-gd php7.4-xml php7.4-mbstring

Depending on project needs, you may Additional PHP modules need to be installed.

5. Update configuration file:
   Open the PHP configuration file php.ini and modify it as needed. Execute the following command to open the configuration file:

sudo nano /etc/php/7.4/cli/php.ini

Some common modifications include adjusting memory limits, setting time zones, etc.

6. Restart the web server:
   After completing the PHP upgrade, you need to restart your web server for the changes to take effect. Depending on the type of web server you are using, execute the following command:

Apache:

sudo service apache2 restart

Nginx:

sudo service nginx restart

Verify whether the upgrade is successful:
Complete the above steps After that, you can verify whether PHP has been successfully upgraded to PHP7.4. Execute the following command in the command line:

php -v

You should be able to see that the PHP version is 7.4.x.

Solving compatibility issues:
In the process of upgrading PHP, you may encounter some compatibility issues. Here are some common problems and their solutions:

1. Update outdated functions and methods:
   In PHP7.4, some old functions and methods have been deprecated or removed. For example, the original mysql_ function has been replaced by the mysqli_ function. Please make sure you use the latest functions and methods in your code.
2. Update outdated syntax and language features:
   PHP7.4 introduces some new syntax and language features, and some outdated or deprecated syntax has also been deleted or modified. Please check your code and update it to comply with PHP7.4 syntax specifications.
3. Check extension module compatibility:
   Before upgrading to PHP7.4, make sure that all extension modules you use are compatible with PHP7.4. Please visit the official extension's website for the latest compatibility information.

Summary:
By following the steps above to upgrade and resolve compatibility issues, you can safely upgrade PHP5.6 to PHP7.4. This results in better performance, more features, and better security, keeping your applications up to date and reliable.

References:

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