JSFiddle - React, Tailwind, and code Playground

HTML

<div id="page">
    <form id="theForm" action="search.php" method="post">
        <input name="first" type="text" />First name<br/>
        <input name="last" type="text" />Last name<br/>    
        <input id="button" type="submit" />
    </form>
</div>

JavaScript

$('#theForm').submit(function() {
      // Add the searching icon
    $("#theForm").html('Searching...<br/><img src="http://i.imgur.com/ZK0sq.gif" />');
      // Make the search request to the PHP page.
    $.post("/ajax_html_echo/", $(this).serialize(), function(result){
        $("#page").html("The search result would be here");
    });
    
    // Cancel the regular submission of the form.
    return false;
});