Repeater Field Shortcode handler

It might be handy to use the repeater custom field of Advanced Custom Fields plugin but it doesn’t work out of the box. So I created an example to give an idea of its usage. This particular shortcode uses a button from Impreza theme to show a set of buttons based on the repeater field:

if ( ! function_exists( 'ch_repeater_shortcode' ) ) {
	/**
	 * Repeater Custom Field handler
	 * use [repeater-field] shortcode to call it from content or Grid Layout
	 *
	 * It has the next attributes style, repeater, title, link,
	 * where the three latest are custom field names
	 */
	add_shortcode( 'repeater-field', 'ch_repeater_shortcode' );
	function ch_repeater_shortcode( $atts ) {
		if ( is_admin() AND ! wp_doing_ajax() ) {
			return FALSE;
		}
		// Parse attributes and apply default values
		$atts = shortcode_atts(
			array(
				'type' => 'btn',
				'style' => '1',
				'repeater' => 'page_repeater',
				'title' => 'page_repeater_text',
				'link' => 'page_repeater_url',
			), $atts
		);

		// Find repeater field
		$repeater = get_field( esc_attr( trim( $atts['repeater'] ) ) );
		if ( ! $repeater ) {
			return FALSE;
		}

		$output = '';

		if ( $atts['type'] == 'btn' ) {
			foreach ( $repeater as $field ) {
				$link = isset( $field[ $atts['link'] ] ) ? esc_url( $field[ $atts['link'] ] ) : NULL;
				if ( $link ) {
					$title = isset( $field[ $atts['title'] ] ) ? esc_attr( $field[ $atts['title'] ] ) : '';
					$output .= '<div class="w-btn-wrapper align_none"><a class="w-btn us-btn-style_' . (int) $atts['style'] . '" href="' . $link . '"><span class="w-btn-label">' . $title . '</span></a></div>';
				}
			}
		}

		return $output;
	}
}