Add and Remove Group Meta Box

<?php
function hhs_get_sample_options() {
	$options = array (
		'Option 1' => 'option1',
		'Option 2' => 'option2',
		'Option 3' => 'option3',
		'Option 4' => 'option4',
	);
	
	return $options;
}
add_action('admin_init', 'hhs_add_meta_boxes', 1);
function hhs_add_meta_boxes() {
	add_meta_box( 'repeatable-fields', 'Repeatable Fields', 'hhs_repeatable_meta_box_display', 'post', 'normal', 'default');
}
function hhs_repeatable_meta_box_display() {
	global $post;
	$repeatable_fields = get_post_meta($post->ID, 'repeatable_fields', true);
	$options = hhs_get_sample_options();
	wp_nonce_field( 'hhs_repeatable_meta_box_nonce', 'hhs_repeatable_meta_box_nonce' );
	?>
	<script type="text/javascript">
	jQuery(document).ready(function( $ ){
		$( '#add-row' ).on('click', function() {
			var row = $( '.empty-row.screen-reader-text' ).clone(true);
			row.removeClass( 'empty-row screen-reader-text' );
			row.insertBefore( '#repeatable-fieldset-one tbody>tr:last' );
			return false;
		});
  	
		$( '.remove-row' ).on('click', function() {
			$(this).parents('tr').remove();
			return false;
		});
	});
	</script>
  
	<table id="repeatable-fieldset-one" width="100%">
	<thead>
		<tr>
			<th width="40%">Name</th>
			<th width="12%">Select</th>
			<th width="40%">URL</th>
			<th width="8%"></th>
		</tr>
	</thead>
	<tbody>
	<?php
	
	if ( $repeatable_fields ) :
	
	foreach ( $repeatable_fields as $field ) {
	?>
	<tr>
		<td><input type="text" class="widefat" name="name[]" value="<?php if($field['name'] != '') echo esc_attr( $field['name'] ); ?>" /></td>
	
		<td>
			<select name="select[]">
			<?php foreach ( $options as $label => $value ) : ?>
			<option value="<?php echo $value; ?>"<?php selected( $field['select'], $value ); ?>><?php echo $label; ?></option>
			<?php endforeach; ?>
			</select>
		</td>
	
		<td><input type="text" class="widefat" name="url[]" value="<?php if ($field['url'] != '') echo esc_attr( $field['url'] ); else echo 'http://'; ?>" /></td>
	
		<td><a class="button remove-row" href="#">Remove</a></td>
	</tr>
	<?php
	}
	else :
	// show a blank one
	?>
	<tr>
		<td><input type="text" class="widefat" name="name[]" /></td>
	
		<td>
			<select name="select[]">
			<?php foreach ( $options as $label => $value ) : ?>
			<option value="<?php echo $value; ?>"><?php echo $label; ?></option>
			<?php endforeach; ?>
			</select>
		</td>
	
		<td><input type="text" class="widefat" name="url[]" value="http://" /></td>
	
		<td><a class="button remove-row" href="#">Remove</a></td>
	</tr>
	<?php endif; ?>
	
	<!-- empty hidden one for jQuery -->
	<tr class="empty-row screen-reader-text">
		<td><input type="text" class="widefat" name="name[]" /></td>
	
		<td>
			<select name="select[]">
			<?php foreach ( $options as $label => $value ) : ?>
			<option value="<?php echo $value; ?>"><?php echo $label; ?></option>
			<?php endforeach; ?>
			</select>
		</td>
		
		<td><input type="text" class="widefat" name="url[]" value="http://" /></td>
		  
		<td><a class="button remove-row" href="#">Remove</a></td>
	</tr>
	</tbody>
	</table>
	
	<p><a id="add-row" class="button" href="#">Add another</a></p>
	<?php
}
add_action('save_post', 'hhs_repeatable_meta_box_save');
function hhs_repeatable_meta_box_save($post_id) {
	if ( ! isset( $_POST['hhs_repeatable_meta_box_nonce'] ) ||
	! wp_verify_nonce( $_POST['hhs_repeatable_meta_box_nonce'], 'hhs_repeatable_meta_box_nonce' ) )
		return;
	
	if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE)
		return;
	
	if (!current_user_can('edit_post', $post_id))
		return;
	
	$old = get_post_meta($post_id, 'repeatable_fields', true);
	$new = array();
	$options = hhs_get_sample_options();
	
	$names = $_POST['name'];
	$selects = $_POST['select'];
	$urls = $_POST['url'];
	
	$count = count( $names );
	
	for ( $i = 0; $i < $count; $i++ ) {
		if ( $names[$i] != '' ) :
			$new[$i]['name'] = stripslashes( strip_tags( $names[$i] ) );
			
			if ( in_array( $selects[$i], $options ) )
				$new[$i]['select'] = $selects[$i];
			else
				$new[$i]['select'] = '';
		
			if ( $urls[$i] == 'http://' )
				$new[$i]['url'] = '';
			else
				$new[$i]['url'] = stripslashes( $urls[$i] ); // and however you want to sanitize
		endif;
	}
	if ( !empty( $new ) && $new != $old )
		update_post_meta( $post_id, 'repeatable_fields', $new );
	elseif ( empty($new) && $old )
		delete_post_meta( $post_id, 'repeatable_fields', $old );
}
?>