Create a WordPress media from file path and attach it to a post.

wordpress-create-media-from-filepath.php

<?php
/**
 * Create media from path.
 *
 * @param string $file_path
 */
function create_media_from_path( $file_path, $post_id = 0 ) {
	// Requires
	require_once( ABSPATH . 'wp-admin/includes/admin.php' );
	require_once( ABSPATH . 'wp-admin/includes/image.php' );

	// Upload media
	$uploaded = wp_upload_bits( 
		basename( $file_path ),
		null, 
		file_get_contents( $file_path )
	);
	
	if ( isset( $upload['error'] ) && $upload['error'] ) {
		return false;
	}

	// Attachment creation
	// Provide a $post_id if you want to attach it
	$filename = $uploaded['file'];

	if ( $filename > '' && $post_id ) {
		$wp_filetype = wp_check_filetype( basename( $filename ), null );

		$attachment = array(
			'post_mime_type' => $wp_filetype['type'],
			'post_title' => preg_replace('/\.[^.]+$/', '', basename( $filename ) ),
			'post_content' => '',
			'post_status' => 'inherit'
		);

		$attach_id = wp_insert_attachment( $attachment, $filename, $post_id );

		$attach_data = wp_generate_attachment_metadata( $attach_id, $filename );
		wp_update_attachment_metadata( $attach_id, $attach_data );

		return $attach_id;
	}
}