you can ajax the request once, but curl you can wait for the execution result of the first to execute the second until your termination condition is met, and then return the result to ajax

first of all, if you need to call more than 3 api to complete this function, it is recommended that you reconsider the design of the function. From the perspective of development, this model has low efficiency and high maintenance rate.
second, if you do not need to handle the results of each successful call, it is recommended that you call calls.php, once and then execute curl calls to different api. three times in this file If you need to process the result of each successful call, you can consider Promise on the js side. For example:

 Promise.all([
            fetchContent(posts.curId),
            fetchContent(posts.next()),
            fetchContent(posts.next())
        ]).then((contents) => {
            // ;
            contents.forEach((content) => {
                console.log(content); 
            });
        }).then(() => {
            console.log(');
        }).catch((err) => { // 
            console.error(err);
        });
        
    function fetchContent(postId) {
        console.log('');
        return new Promise((resolve, reject) => {
            window.fetch(`http://mydomain.com/posts/${postId}`,{
                    method: 'GET'
            }).then((response) => {
                resolve(response.text());
            }, (err) => {
                reject(err);
            });
        });
    };

all you need is await and async.
you can write it like this:

  
 are you sure you can cross-domain?