Try working through the source code of a plugin such as PayPal Framework.
From your question, the WP side is fairly trivial, but you should study general PayPal tutorials to understand the API, for example, here’s the first search result from Google for PayPal API tutorial: Using PayPal’s IPN with PHP
Also some additional helpful info can be found here.
Related Posts:
- How to change a user’s role?
- How to get role of user
- How do I programmatically set default role for new users?
- What do unfiltered_html and unfiltered_upload actually filter?
- Temporary capability for current_user_can()
- How to update role capabilities
- How to loop through each user id?
- Code needed to only show users own posts in a multi-user account
- Ordering users of a specific role by last name
- Restrict Author to pick from media library, but not upload media
- how to add custom user capabilities using add_user_meta or something else?
- Remove Ability for Administrators to Delete Administrators
- Order users by custom user meta
- List total number of users that are authors
- I need to assign a role to visitors/guests
- Auto Delete Users (auto_delete_users)
- New Roles and Capabilities in WordPress
- WordPress Super Admin
- How to get all users with Author role capabilities?
- How to ‘unpublish’ or ‘hide’ posts when user role changes?
- Can’t manage to make translate_user_role() work
- Add Role inherits?
- similar to Editor can create any new user except administrator
- How to check if a role has a specific capability
- I am adding a new class to my body tag if the logged in user is subscriber, need help
- Expire a user’s secondary role after X days from it being allocated
- Can a user with admin role get ‘Sorry, you are not allowed to move this item to the Trash’ error when trashing a post?
- Making shortcode of filtered number of comments by user role
- How to stop contributors editing post type but allowing them to edit a custom post type?
- Allow Block Editing By User Role
- Capabilites not working [closed]
- WordPress missing user roles on local dev machine. Live site works fine
- Programmatically allow a non-author to edit a post based custom meta field
- Create Super Admin that cant be deleted
- Customizer – Allow user editor to change website title and tagline
- Query users which have same dynamically generated roles as the current user
- change role of wordpress users when they edit profile
- Adding Capabilities to a WordPress User Account
- Change post status based on user role
- Display User Role Next To Comment
- Pending status by default for a specific role
- Getting a role based on a localized role name
- Allow an editor to change the author
- How do I restrict user access to plugins?
- Parent User and Child User – relate users
- Admin User Role Unable to See Private Posts
- how to set any post creation for pending status and let the admin approve it first?
- How to give remove role editing permission from user
- How to have kind of a technical writer role in wp website
- Assigning certain authors to specific editors
- Undo User Role Name Change
- add_role user capability not working
- How to make the Newsletter plugin visible to users with author privileges?
- WP welcome email depending on user role
- Allow user role “salesman” to view only “client” role users
- Limit a user to have access to only specified pages?
- How can I promote a user to a network administrator?
- read_private_pages capability not working for new role
- How to get a users list by who created them?
- Updater user with multiple roles
- Custom user types getting html sanitized in posts
- Is there a Capability that checks as true for non-logged in users?
- Hiding custom theme functionality using capabilities
- Use PHP code to create custom user roles. Call it once?
- custom plugin not visible to some user roles
- How to write conditions based on user capabilities not on user role?
- What Capability is required to let a role RUN code in Edit Theme?
- remove_cap nothing changes
- get_post_meta with related user
- How to change a user’s role depending on date registered?
- Need to block user role from accessing bbPress all together
- Show special backend content for certain roles
- Retrieve user roles but exclude default roles
- Why can my subscribers create new posts for review?
- Custom Role read_private_posts Not Working
- Learndash change user role after completing the course
- Disabled delete_others_posts if post is from admin
- How to hide Add new Term area for taxonomy terms for specific role (Client)
- Saving user meta “member_id” based on user role
- Change logo url based on WP user role
- show the author’s role along with the name in the single.php
- Display specific post categories to specific user roles
- Publishing post strips custom html element when user is not admin
- Role and Capabilities: How do I allow user role to access theme options without enabling ‘manage_options’?
- How to Enable registration email for a custom user role?
- How can I add the ability for a user to add/edit administrators?
- Allow signed in users (subscribers) to see their drafts
- How to sync user database with “user role editor” plugin enabled
- add user role selection to registration form [duplicate]
- Need to create admin user without capability to create user
- Assign specific editor with custom user meta “A” to all authors with custom user meta “A” and exclude all other author access
- Grant access to admin menu?
- Give editor ability to edit custom settings without access to Main Settings
- I want this code to work only for Authors AND Contributors
- Disable Woocommerce checkout based on user role [closed]
- Remove_role not working, gives “Call to undefined method stdClass::remove_role()”
- Adding a new role with administrator’s capabilities
- Get users by rôle in a list
- Role Scoper, don’t allow other users to see pending posts
- WordPress show content if current user get spesific role and spesific meta value