将数据从PHP文件写入json文件

I have a test.php page which displayes three has 3 "Add Link" buttons, on clicking the buttons the user sees a popup window. In the window he adds the link. Once the link is added , the base page will change from "Add link" button to hyperlink with the new link. Now, I have to pass the new link I receive from the user from test.php to links.php using an ajax call. Links.php has to have a JSON code to write the link to another file called first.json. first.jason will have key value pair for variable and link. I would have to retrieve the value from .json file later and reconstruct into an array, update the corresponding variable and save it back.I have a test.php page which displayes three ha