functions.php

Connecting GForms to ACF Gallery by Joshua Nelson

<?php

/**
* Attach images uploaded through Gravity Form to ACF Gallery Field
*
* @author Joshua David Nelson, josh@joshuadnelson.com
* @return void
*/

add_filter( "gform_after_submission_3", 'jdn_set_post_acf_gallery_field', 10, 2 );
function jdn_set_post_acf_gallery_field( $entry, $form ) {
	$gf_images_field_id = 4; // the upload field id
	$acf_field_id = 'field_5356e6a603b30'; // the acf gallery field id
	// get post
	if( isset( $entry['post_id'] ) ) {
		$post = get_post( $entry['post_id'] );
		if( is_null( $post ) )
			return;
		} else {
			return;
		}
	// Clean up images upload and create array for gallery field
	if( isset( $entry[ $gf_images_field_id ] ) ) {
		$images = stripslashes( $entry[ $gf_images_field_id ] );
		$images = json_decode( $images, true );
		if( !empty( $images ) && is_array( $images ) ) {
			$gallery = array();
			foreach( $images as $key => $value ) {
				if( function_exists( 'jdn_create_image_id' ) )
					$image_id = jdn_create_image_id( $value, $post->ID );
				if( $image_id ) {
					$gallery[] = $image_id;
				}
			}
		}
	}
	// Update gallery field with array
	if( ! empty( $gallery ) ) {
		update_field( $acf_field_id, $gallery, $post->ID );
	// Updating post
	wp_update_post( $post );
	}
} 


/**
* Other function needed. This is to get image attachment ID
*
* @author Joshua David Nelson, josh@joshuadnelson.com
* Source: https://gist.github.com/joshuadavidnelson/164a0a0744f0693d5746
*/

function jdn_create_image_id( $image_url, $parent_post_id = null ) {
	
	if( !isset( $image_url ) )
		return false;
		
	// Cache info on the wp uploads dir
	$wp_upload_dir = wp_upload_dir();
	// get the file path
	$path = parse_url( $image_url, PHP_URL_PATH );
	
	// File base name
	$file_base_name = basename( $image_url );
	
	// Full path
	$home_path = get_home_path();
	$home_path = untrailingslashit( $home_path );
	$uploaded_file_path = $home_path . $path;
	
	// Check the type of file. We'll use this as the 'post_mime_type'.
	$filetype = wp_check_filetype( $file_base_name, null );
	
	// error check
	if( !empty( $filetype ) && is_array( $filetype ) ) {
		// Create attachment title
		$post_title = preg_replace( '/\.[^.]+$/', '', $file_base_name );
		
		// Prepare an array of post data for the attachment.
		$attachment = array(
			'guid' => $wp_upload_dir['url'] . '/' . basename( $uploaded_file_path ),
			'post_mime_type' => $filetype['type'],
			'post_title' => esc_attr( $post_title ),
			'post_content' => '',
			'post_status' => 'inherit'
		);
		
	// Set the post parent id if there is one
	if( !is_null( $parent_post_id ) )
		$attachment['post_parent'] = $parent_post_id;
		
	// Insert the attachment.
	$attach_id = wp_insert_attachment( $attachment, $uploaded_file_path );
	
	//Error check
	if( !is_wp_error( $attach_id ) ) {
		//Generate wp attachment meta data
		if( file_exists( ABSPATH . 'wp-admin/includes/image.php') && file_exists( ABSPATH . 'wp-admin/includes/media.php') ) {
			require_once( ABSPATH . 'wp-admin/includes/image.php' );
			require_once( ABSPATH . 'wp-admin/includes/media.php' );
			$attach_data = wp_generate_attachment_metadata( $attach_id, $uploaded_file_path );
			wp_update_attachment_metadata( $attach_id, $attach_data );
		} // end if file exists check
	} // end if error check
	return $attach_id;
	} // end if $$filetype
} // end function get_image_id 

?>

Rocky, see the response on the blog post. I made a change to the id function and there is another gist that might work for you - my example assumed you were creating a new post on submit (so it needed a post_id in the entry object).