Creates a custom field in WordPress using Custom Metadata Manager and uses custom display and sanitize callbacks

custom-metadata_custom-display-and-sanitize.php

<?php
x_add_metadata_field('x_fieldCustomList2', array( 'post' ), array(
	'label' => 'Post Action Items (With Links!)'
	, 'display_callback' => 'fieldCustomList2_display'
	, 'sanitize_callback' => 'fieldCustomList2_sanitize'
));

function fieldCustomList2_display( $field_slug, $field, $object_type, $object_id, $value ) {
	$value = (array) $value;
	$field_class = sprintf( 'field-%s', $field_slug );
	$count = 0;
	?>
	<?php if( ! empty( $value ) ) : ?>
		<?php foreach( $value as $v ) : ?>
			<?php
			$text = isset( $v['text'] ) ? $v['text'] : '';
			$url = isset( $v['url'] ) ? $v['url'] : '';
			?>
			<div class="f2_my-list-item">
				<label>Text</label>
				<input type="text" name="<?php echo $field_slug; ?>_text[]" value="<?php echo esc_attr( $text ); ?>" />
				
				<label>URL</label>
				<input type="text" name="<?php echo $field_slug; ?>_url[]" value="<?php echo esc_attr( $url ); ?>" />
				
				<?php if( $count > 0 ) : ?>
					<a href="#" class="f2_btn-del-list-item hide-if-no-js" style="color:red;">Delete</a>
				<?php endif; ?>
				<?php $count++; ?>
			</div>
		<?php endforeach; ?>
	<?php else : ?>
		<input type="text" name="<?php $field_slug; ?>[]" value="" />
	<?php endif; ?>
	<p><a href="#" class="f2_btn-add-list-item hide-if-no-js">+ Add New</a></p>
	
	<script>
	;(function($) {
		$('.f2_btn-add-list-item').click(function(e) {
			e.preventDefault();
			var $last = $('.f2_my-list-item:last');
			var $clone = $last.clone();
			
			$clone
				.insertAfter($last)
				.find(':input')
					.val('')
				;
		});
		$('.f2_btn-del-list-item').live('click', function(e) {
			e.preventDefault();
			$(this).parent().remove();
		});
	})(jQuery);
	</script>
	<?php
}

function fieldCustomList2_sanitize( $field_slug, $field, $object_type, $object_id, $value ) {
	$values = array();
	$text_key = $field_slug . '_text';
	$url_key = $field_slug . '_url';
	
	if( isset( $_POST[$text_key] ) ) {
		$count = 0;
		foreach( (array) $_POST[$text_key] as $text ) {
			$url = isset( $_POST[$url_key][$count] ) ? $_POST[$url_key][$count] : '';
			if( $text || $url ) {
				array_push( $values, array(
					'text' => $text
					, 'url' => $url
				) );
			}
			$count++;
		}
	}
	
	return $values;
}
?>