What could be causing the JavaScript code to not execute in the process.php file, and how can I resolve this issue?

Description: I’m working on a PHP script that should automatically click an email link using JavaScript. The code works fine in a separate test.php file, but in process.php, the JavaScript doesn’t execute. Below is the relevant code:

<?php
include_once 'libs/load.php';
if (isset($_POST['command'])) {
    $command = trim($_POST['command']);
    handleCommand($command);
}

function handleCommand($command)
{
    switch ($command) {
        case 'email':
            $email = "[email protected]";
            echo "<html><body>";
            echo "<a id="emailLink" href="mailto:$email" style="color: rgb(5, 206, 145);">$email</a>";
            echo "<script type="text/javascript">
                    document.addEventListener('DOMContentLoaded', function() {
                        console.log('JavaScript is running');
                        alert('JavaScript is running');
                        document.getElementById('emailLink').click();
                    });
                  </script>";
            echo "</body></html>";
            break;
        default:
            echo "---n";
            echo "Unknown command: $commandn";
            echo "---";
            break;
    }
}
?>