How to Add Images to Media Library after Uploading them in PHP Programmatically

When you upload files from WordPress admin area, they will automatically appear in Media > Library. But what if you want to create a custom file uploader specially for your website visitors?

Step 1. As usual, we Begin with HTML Form

<form action="<?php echo get_stylesheet_directory_uri() ?>/process_upload.php" method="post" enctype="multipart/form-data">
	Your Photo: <input type="file" name="profilepicture" size="25" />
	<input type="submit" name="submit" value="Submit" />
</form>

What is important to remember here?

• I placed the PHP file process_upload.php into the theme directory, if you would like to move it to the other location, do not forget to make changes in the next piece of code on line 4 (I mean code in Step 2).
• The form must have enctype="multipart/form-data" attribute. Many forget about it.

You can also create a shortcode for this form, just insert this to the functions.php:

add_shortcode( 'misha_uploader', 'misha_uploader_callback' );

function misha_uploader_callback(){
	return '<form action="' . get_stylesheet_directory_uri() . '/process_upload.php" method="post" enctype="multipart/form-data">
	Your Photo: <input type="file" name="profilepicture" size="25" />
	<input type="submit" name="submit" value="Submit" />
	</form>';
}

Now you can use just [misha_uploader] in the editor.

Step 2. Process the Uploaded File in PHP and Add the File Metadata to WordPress Database

This is process_upload.php file that I decided to create in my current theme directory.

<?php

// WordPress environment
require( dirname(__FILE__) . '/../../../wp-load.php' );

$wordpress_upload_dir = wp_upload_dir();
// $wordpress_upload_dir['path'] is the full server path to wp-content/uploads/2017/05, for multisite works good as well
// $wordpress_upload_dir['url'] the absolute URL to the same folder, actually we do not need it, just to show the link to file
$i = 1; // number of tries when the file with the same name is already exists

$profilepicture = $_FILES['profilepicture'];
$new_file_path = $wordpress_upload_dir['path'] . '/' . $profilepicture['name'];
$new_file_mime = mime_content_type( $profilepicture['tmp_name'] );

if( empty( $profilepicture ) )
	die( 'File is not selected.' );

if( $profilepicture['error'] )
	die( $profilepicture['error'] );
	
if( $profilepicture['size'] > wp_max_upload_size() )
	die( 'It is too large than expected.' );
	
if( !in_array( $new_file_mime, get_allowed_mime_types() ) )
	die( 'WordPress doesn\'t allow this type of uploads.' );
	
while( file_exists( $new_file_path ) ) {
	$i++;
	$new_file_path = $wordpress_upload_dir['path'] . '/' . $i . '_' . $profilepicture['name'];
}

// looks like everything is OK
if( move_uploaded_file( $profilepicture['tmp_name'], $new_file_path ) ) {
	

	$upload_id = wp_insert_attachment( array(
		'guid'           => $new_file_path, 
		'post_mime_type' => $new_file_mime,
		'post_title'     => preg_replace( '/\.[^.]+$/', '', $profilepicture['name'] ),
		'post_content'   => '',
		'post_status'    => 'inherit'
	), $new_file_path );

	// wp_generate_attachment_metadata() won't work if you do not include this file
	require_once( ABSPATH . 'wp-admin/includes/image.php' );

	// Generate and save the attachment metas into the database
	wp_update_attachment_metadata( $upload_id, wp_generate_attachment_metadata( $upload_id, $new_file_path ) );

	// Show the uploaded file in browser
	wp_redirect( $wordpress_upload_dir['url'] . '/' . basename( $new_file_path ) );

}

Optionally we can set the third parameter of the wp_insert_attachment() as a parent post ID, and set the featured image of this post with set_post_thumbnail().

https://rudrastyh.com/wordpress/how-to-add-images-to-media-library-from-uploaded-files-programmatically.html