To save a PHP file in Mac TextEdit, follow these steps:

1. Open TextEdit and create a new file.
2. Type your PHP code in the file.
3. Go to the “Format” menu and select “Make Plain Text”. This will ensure that TextEdit does not add any formatting to your PHP code.
4. Go to the “File” menu and select “Save As”.
5. In the “Save As” window, give your file a name and make sure the “File Format” dropdown is set to “PHP Script”.
6. Click “Save”. Your PHP file is now saved and ready to be run on a web server.

Note: To run PHP code, you will need to have a web server installed on your computer. You can use a tool like MAMP (for Mac) or XAMPP (for Windows) to set up a local web server on your machine. Once you have a web server installed, you can place your PHP files in the server’s document root directory and access them through your web browser by entering the file’s URL in the address bar.