It sounds as though your include file activate.php does not have the opening/closing php tags. Be sure to open activate.php and ensure it has the <?php at the beginning of the file, and the ?> at the end.
Related Posts:
- How to include class from addon after to be sure one class exists in the main plugin?
- include wp-blog-header not working on MAMP
- get_option() not returning expected value from plugin
- include php file if page_id matches
- can’t access some WordPress function from my plugin
- I’m including a html file in my plugin, but it can’t find its css or js files
- Including content into an add_shortcode() function
- How to include files in the loop via ajax
- Using WP_PLUGIN_DIR for include file
- Objective Best Practices for Plugin Development? [closed]
- add_menu_page() with different name for first submenu item
- Autoloading & Namespaces in WordPress Plugins & Themes: Can it Work?
- How to include PHP files in plugins the correct way
- How can I add an image upload field directly to a custom write panel?
- A tool to analyze rewrite rules? [closed]
- Difference Between Filter and Action Hooks?
- framework for plugin/theme options panel? [closed]
- Creating a table in the admin-style?
- How can you check if you are in a particular page in the WP Admin section? For example how can I check if I am in the Users > Your Profile page?
- Settings API with arrays example
- How to get the path to the current theme?
- How to make a plugin require another plugin?
- ajaxurl not defined on front end
- What process do you use for WordPress development? [closed]
- What’s the difference between term_id and term_taxonomy_id
- Should I use wpdb prepare?
- Why does WordPress use outdated jQuery v1.12.4?
- Post meta vs separate database tables
- Is there any plugin development framework
- Is it possible to reuse wp.media.editor Modal for dialogs other than media
- How to add a javascript snippet to the footer that requires jQuery
- Enhance Media Manager for Gallery
- How do I create a custom role capability?
- How do I add CSS options to my plugin without using inline styles?
- How do i best handle custom plugin page actions?
- Adding Custom Text Patterns in the WP 4.5 Visual Editor
- Automatically determine minimum WordPress version required for a plugin?
- What is the advantage of using wp_mail?
- How to make a WordPress plugin translation ready?
- How many times will this code run? (or, how rich is grandma?)
- How to create an API for my plugin?
- Is it ever okay to include inline CSS in plugins?
- Plugins in symlinked directories?
- How to override existing plugin action with new action
- How to include a file using get_template_part() in a plugin?
- Add custom TinyMCE 4 Button, Usable since WordPress 3.9-beta1
- How to store username and password to API in wordpress option DB?
- body_class hook for admin pages
- “Error: Options Page Not Found” on Settings Page Submission for an OOP Plugin
- Is it mandatory to use $wpdb->prefix in custom tables
- Which hook should be used to add an action containing a redirect?
- add_action hook for completely new post?
- Why does WordPress add 0 (zero) to an Ajax response?
- What should I use instead of WP_CONTENT_DIR and WP_PLUGIN_DIR?
- How to enqueue JavaScripts in a plugin
- In Which Contexts are Plugins Responsible for Data Validation/Sanitization?
- Plugin Form Submission Best Practice
- How to redirect to settings page once the plugin is activated?
- Is get_option function cached?
- Should Plugin Folders Include a Blank index.php File?
- Unit testing for plugin development
- Methods of Integrating Plugin Data with Themes
- What is the wordpress wp-includes folder for?
- WordPress Update Plugin Hook/Action? Since 3.9
- How to include jQuery and JavaScript files correctly?
- How come `wp_options` table does not have an index on `autoload`?
- PHP error with shortcode handler from a class
- Update Option Stored in Multi-Dimensional Array
- check if Gutenberg is currently in use
- Best way to abort plugin in case of insufficient PHP version?
- WordPress Plugin Development – Headers Already Sent Message
- WP 3.3 How to Add Menu Items to the Admin Bar?
- dbDelta not creating tables
- Custom Widget function in Plugin not working?
- Passing arguments to a admin menu page callback?
- Single functions.php or split into many small files?
- Get page content using slug
- $_POST form request with admin-post
- How to fork a plugin?
- How can I configure Docker for developing and deploying a custom theme?
- How to include wp-load.php from any location?
- Correct way to enqueue jquery-ui
- Where to store PHP files created by plugin / themes
- How to echo the_excerpt without the P tag wrapper?
- How can I update a wordpress plugin from a Git repository (github)
- What are the advantages to the Settings API?
- Add screen options to custom admin pages
- Strategy On Building Plugin Using Eclipse
- How to add sub-menu to a menu generated by wp_nav_menu by using plugin
- Is There a Plugin Life Cycle Documentation?
- What do you think about custom designed plugin/theme options UIs?
- No Error Log File, no debug info
- Is it necessary to bump a plug-in’s version if you’re just updating the “Tested up to” attribute?
- Adding Widget form fields dynamically
- How to debug a plugin with Xdebug?
- WP_Query leaking absurd amounts of memory
- What is the difference between $post_id and get_the_ID()?
- How do I improve this admin query snippet to avoid generating duplicate results on non-meta searches?
- Where to store plugin settings fields
- Add self-closing shortcode button to TinyMCE in WP 4.6