There are a few ways to split a form into multiple steps, but one of the easiest is to use JavaScript or jQuery to hide and show different sections of the form based on the user’s progress. Here’s an example using jQuery:

1. Create your form as one long HTML document, but divide it into sections using divs. For example:

<form>
  <div id="step1">
    <label for="name">Name:</label>
    <input type="text" id="name" name="name">
    <label for="email">Email:</label>
    <input type="email" id="email" name="email">
    <button type="button" id="continue1">Continue</button>
  </div>
  <div id="step2" style="display:none;">
    <label for="address">Address:</label>
    <input type="text" id="address" name="address">
    <label for="city">City:</label>
    <input type="text" id="city" name="city">
    <button type="button" id="continue2">Continue</button>
  </div>
  <div id="step3" style="display:none;">
    <label for="phone">Phone:</label>
    <input type="text" id="phone" name="phone">
    <label for="submit"></label>
    <button type="submit">Submit</button>
  </div>
</form>

1. Add the jQuery library to your HTML file and add a script to hide and show the different sections of the form. For example:

<script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
<script>
  $(document).ready(function(){
    $("#continue1").click(function(){
      $("#step1").hide();
      $("#step2").show();
    });
    $("#continue2").click(function(){
      $("#step2").hide();
      $("#step3").show();
    });
  });
</script>

1. To handle the form submission in PHP, you can use the $_POST variable to access the form data and process it as needed. For example:

if(isset($_POST['name']) && isset($_POST['email']) && isset($_POST['address']) && isset($_POST['city']) && isset($_POST['phone'])) {
    // form was submitted, process the data
    $name = $_POST['name'];
    $email = $_POST['email'];
    $address = $_POST['address'];
    $city = $_POST['city'];
    $phone = $_POST['phone'];
    // do something with the data, such as insert it into a database
}

This is just one example of how you can split a form into multiple steps. You can customize the code to suit your specific needs and use different techniques such as progress bars or breadcrumb navigation to guide the user through the form.