<form method="post" action="https://php.tomgdow.com" id="form_one">
    <div>
        <!-- <label for="name">Name</label> -->
        <input type="hidden" id="name" name="param1" value="Hello">
        <input type="hidden" id="hidden" name="param2" value="You clicked the button!">
    </div>
    <div>
        <input id="mybtn" type="image" src="../images/myButton2.png" alt="Blue Button">
    </div>
    <fieldset class="output">
        <div>
            <output for="hidden1" id="out-hidden1"></output>
        </div>
        <div>
            <output for="hidden2" id="out-hidden2"></output>
        </div>
    </fieldset>
</form>

    async function sendData() {

        const formData = new FormData(form_one);

        try {
            const response = await fetch("https://php.tomgdow.com", {
                method: "POST",
                body: formData
            });

            let result = await response.text();
            console.log(result);
            let responseArray = result.split('&');
            document.getElementById('out-hidden1').value = responseArray[0];
            document.getElementById('out-hidden2').value = responseArray[1];

        } catch (e) {
            console.error(e);
        }
    }

    document.getElementById('form_one').addEventListener('submit', function (event) {

        event.preventDefault();

        sendData();

    });


    document.getElementById("mybtn").addEventListener('mouseleave', function () {

        document.getElementById('out-hidden1').style.backgroundColor = "black"
        document.getElementById('out-hidden1').style.color = "white"
        document.getElementById('out-hidden2').style.backgroundColor = "black"
        document.getElementById('out-hidden2').style.color = "white"
    })

    document.getElementById("mybtn").addEventListener('mouseover', function () {

        document.getElementById('out-hidden1').style.backgroundColor = "revert"
        document.getElementById('out-hidden1').style.color = "revert"
        document.getElementById('out-hidden1').value = "";
        document.getElementById('out-hidden2').style.backgroundColor = "revert"
        document.getElementById('out-hidden2').style.color = "revert"
        document.getElementById('out-hidden2').value = "";
    })

                            

// index.php (server)

<?php
  echo  
     htmlspecialchars($_POST["param1"])."&"
     .htmlspecialchars($_POST["param2"])."&"
     .htmlspecialchars($_SERVER['HTTP_HOST']);
?>