The php.ini file is the master configuration file for PHP on your hosting server. It controls how PHP behaves, determining settings like memory limits, file upload sizes, error reporting, and security features. Every time PHP runs, it reads this file to apply your specified configurations.

You can locate your php.ini file in your hosting account's root directory (often public_html or www). Some hosts allow multiple versions; check your control panel (like cPanel) for "PHP Selector" or "PHP Version" tools.

Common settings you might adjust include:

• upload_max_filesize & post_max_size: Control maximum upload size.
• memory_limit: Sets the maximum memory a script can consume.
• max_execution_time: Defines how long a script runs before timing out.
• display_errors: Shows or hides error messages (set to Off on live sites).

To modify php.ini:

1. Create a backup of the original file.
2. Edit the file using a plain text editor in your hosting File Manager.
3. Change values using the format: directive = value
4. Save the file and restart your web server for changes to take effect.

Pro Tip: Many hosts support custom .user.ini files in specific directories for per-folder configuration overrides, which is often simpler and safer.

Always test changes in a staging environment first. Incorrect settings can cause website errors or security vulnerabilities. If unsure, consult your hosting provider's support team for guidance on optimal configurations for your applications.