There are several popular social sharing platforms available that can be integrated into a PHP website. Here are some examples:

1. Facebook Share: The Facebook Share button allows users to share a specific URL on their Facebook timeline or send it to friends via private message. You can use the Facebook Share button API to generate the share button code and track the number of shares.

2. Twitter Share: The Twitter Share button lets users tweet a specific URL with a pre-populated message. You can generate the Twitter Share button code using the Twitter for Websites API, and track the number of shares using their analytics platform.

3. Pinterest Save: The Pinterest Save button allows users to save an image or URL to their Pinterest boards. You can generate the Save button code using the Pinterest Save Button API and track the number of saves using their analytics platform.

4. LinkedIn Share: The LinkedIn Share button lets users share a specific URL on their LinkedIn feed. You can generate the Share button code using the LinkedIn Share API and track the number of shares using their analytics platform.

5. WhatsApp Share: The WhatsApp Share button allows users to share a specific URL or message with their contacts on WhatsApp. You can generate the Share button code using the WhatsApp Click to Chat API.

To integrate these social sharing platforms into a PHP website, you’ll need to include the relevant SDKs or APIs provided by each platform. These SDKs or APIs will provide you with the necessary code to generate the share buttons, track the number of shares, and handle any authentication or authorization required by the platform.