Cacher is the code snippet organizer for pro developers

<?php
/*
uses: acf gallery field
launches gallery from single button
*/
function service_gallery() {
	
	global $post;
	
	$photos = get_field( 'gallery' );
	
	if( empty( $photos ) )
		return;
	
	$output = '';
	
	// print out all the photo links
					
	foreach( $photos as $key => $photo ) {
						
		$button = '';
		$class = '';
						
		if ( !$key ) {
			// We are at the first element
			$button = '<span class="view-gallery">View Gallery</span>';
			$class = ' gallery button';
		}
		
		$attachment_id = $photo['ID'];
										
		$lightbox = wp_get_attachment_image_src( $attachment_id, 'lightbox', array() );
								
		$output .= sprintf( '<a href="%s" class="foobox%s" rel="gallery-%s" title="%s">%s</a>', $lightbox[0], $class, get_the_ID(), esc_html( $photo['caption'] ), $button );	
		
	}
	
	return $output;				
}