Example

<?php
$form = new Form('plugins-popover-form-1', 'vertical');

$form->addInput('text', 'user-name-popover', '', 'username', 'required');
$form->addInput('email', 'user-email-popover', '', 'e-mail address', 'required');
$form->centerContent();
$form->addBtn('button', 'cancel-btn-popover', 1, 'Cancel', 'class=btn btn-default', 'submit_group');
$form->addBtn('submit', 'submit-btn-popover', 1, 'Send ', 'class=btn btn-success', 'submit_group');
$form->printBtnGroup('submit_group');

$form->popover();
?>

<div class="d-flex justify-content-between">
    <button data-popover-trigger="plugins-popover-form-1" class="btn btn-warning">Open the popover form</button>
    <button data-popover-trigger="plugins-popover-form-1" data-animation="perspective" data-backdrop="true" data-theme="light-border" class="btn btn-primary text-white">Open the same popover form with different settings</button>
</div>
<div class="hide hidden d-none">
    <div id="plugins-popover-form-1-content">
        <form id="plugins-popover-form-1" class="form-horizontal popover-form">
<div class="bs5-form-stacked-element mb-3">
	<label for="user-name-popover" class="form-label">
		username <sup class="text-danger">* </sup>
	</label>
	<input id="user-name-popover" name="user-name-popover" type="text" value="" required class="form-control">
</div>
<div class="bs5-form-stacked-element mb-3">
	<label for="user-email-popover" class="form-label">
		e-mail address <sup class="text-danger">* </sup>
	</label>
	<input id="user-email-popover" name="user-email-popover" type="email" value="" required class="form-control">
</div>
<div class="mb-3 phpfb-centered">
	<div class="btn-group">
		<button type="button" name="cancel-btn-popover" value="1" class="btn btn-default">
			Cancel
		</button>
		<button type="submit" name="submit-btn-popover" value="1" class="btn btn-success">
			Send 
		</button>
	</div>
</div>
        </form>
    </div>
</div>