Ultimate WordPress Plugin Main File

How to leave legacy technologies behind

Source code in plugin-name.php needs PHP 7 which is present on more than 90% of WordPress installations.

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Parts of plugin main file

• Header comment
• PHP strict types
• PHP namespaces
• Prevent direct execution
• Load autoloader
• Prevent double activation
• Define constant values in an immutable container
• Load translations
• Check requirements
  • PHP and WordPress minimum version
  • Multisite installation
  • Other plugins
  • Current theme
  • Composer packages
• Hook plugin activation functions
• Support WP-CLI
• Display admin notice and deactivate plugin on error

💡 Anything else goes into a separate file.

What to avoid

• ❌ Global constants
• ❌ Global functions
• ❌ Classes without namespace
• ❌ Loading PHP files with require
• ❌ Code with side-effects outside the main file
• ❌ Immediate execution without add_action in the main file
• ❌ Conditional function or class definitions

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Installation

1. Get the plugin ZIP from ...
2. Upload to Plugins / Add new / Upload /wp-admin/plugin-install.php?tab=upload

Usage

1. Adjust settings ...
2. Or add a hook add_filter('project/enable', '__return_true'); to functions.php