Programmatically Add Images to Media Library

Recently I built a plugin for a client that utilized a front-end Gravity Form submission to create media file entries and link them to posts. Part of the plugin was the ability to take a file uploaded to the server (in this case, by Gravity Forms) and use that url to create a media entry, so it appears within the media library. Below is the code to add an image to the media library programmatically:

	<?php
	/**
	* Create the image attachment and return the new media upload id.
	*
	* @author Joshua David Nelson, [email protected]
	*
	* @since 03.29.2017 updated to a class, utilizing code from Takuro Hishikawa's gist linked below.
	*
	* @see https://gist.github.com/hissy/7352933
	*
	* @see http://codex.wordpress.org/Function_Reference/wp_insert_attachment#Example
	*
	* @link https://joshuadnelson.com/programmatically-add-images-to-media-library/
	*/
	class JDN_Create_Media_File {

	var $post_id;
	var $image_url;
	var $wp_upload_url;
	var $attachment_id;

	/**
	* Setup the class variables
	*/
	public function __construct( $image_url, $post_id = 0 ) {

	// Setup class variables
	$this->image_url = esc_url( $image_url );
	$this->post_id = absint( $post_id );
	$this->wp_upload_url = $this->get_wp_upload_url();
	$this->attachment_id = $this->attachment_id ?: false;

	return $this->create_image_id();

	}

	/**
	* Set the upload directory
	*/
	private function get_wp_upload_url() {
	$wp_upload_dir = wp_upload_dir();
	return isset( $wp_upload_dir['url'] ) ? $wp_upload_dir['url'] : false;
	}

	/**
	* Create the image and return the new media upload id.
	*
	* @see https://gist.github.com/hissy/7352933
	*
	* @see http://codex.wordpress.org/Function_Reference/wp_insert_attachment#Example
	*/
	public function create_image_id() {

	if( $this->attachment_id )
	return $this->attachment_id;

	if( empty( $this->image_url ) \|\| empty( $this->wp_upload_url ) )
	return false;

	$filename = basename( $this->image_url );

	$upload_file = wp_upload_bits( $filename, null, file_get_contents( $this->image_url ) );

	if ( ! $upload_file['error'] ) {
	$wp_filetype = wp_check_filetype( $filename, null );
	$attachment = array(
	'post_mime_type' => $wp_filetype['type'],
	'post_parent' => $this->post_id,
	'post_title' => preg_replace('/\.[^.]+$/', '', $filename),
	'post_content' => '',
	'post_status' => 'inherit'
	);
	$attachment_id = wp_insert_attachment( $attachment, $upload_file['file'], $this->post_id );

	if( ! is_wp_error( $attachment_id ) ) {

	require_once( ABSPATH . "wp-admin" . '/includes/image.php' );
	require_once( ABSPATH . 'wp-admin/includes/media.php' );

	$attachment_data = wp_generate_attachment_metadata( $attachment_id, $upload_file['file'] );
	wp_update_attachment_metadata( $attachment_id, $attachment_data );

	$this->attachment_id = $attachment_id;

	return $attachment_id;
	}
	}

	return false;

	} // end function get_image_id
	}

	// Example Usage

	// Add an unattached image to the media library
	$image_url = 'http://someimageurl';
	$create_image = new JDN_Create_Media_File( $image_url );
	$image_id = $create_image->attachment_id;

	// Add image and attach to a post
	$post_id = '3'; // the id of the post
	$create_image = new JDN_Create_Media_File( $image_url, $post_id );
	$image_id = $create_image->attachment_id;