wp_image_upload.php

<?php
    public function pfmEditProfile()
        {   	
            if (!isset($_POST['pfmEditProfile']) || !wp_verify_nonce($_POST['pfmEditProfile'], 'pfmEditProfile-nonce')) {
                die("You are not allowed to submit data.");
            }

            if ( ! function_exists( 'wp_handle_upload' ) ) {
                require_once( ABSPATH . 'wp-admin/includes/file.php' );
            }

            $file_return = wp_handle_upload( $_FILES['profile_picture'], array('test_form' => false ) );

            if( isset( $file_return['error'] ) || isset( $file_return['upload_error_handler'] ) ) {
                return false;
            }

            $attachment_id = (new PfmUpload())->attachFile($file_return);

            if (empty($attachment_id)) {
                return false;
            } 

            update_user_meta( get_current_user_id(), 'photo', $attachment_id );

            wp_redirect($_POST['_wp_http_referer']);
            exit();
        }
    public static function attachFile(array $file, $post_id = false)
    {
        $url        = $file['url'];
        $type       = $file['type'];
        $file       = $file['file'];

        $title      = preg_replace('/\.[^.]+$/', '', basename($file));
        $parent     = (int) absint($post_id) > 0 ? absint($post_id) : 0;
        $attachment = array(
            'post_mime_type' => $type,
            'guid'           => $url,
            'post_parent'    => $parent,
            'post_title'     => $title,
            'post_content'   => '',
        );
        $id = wp_insert_attachment($attachment, $file, $parent);
        if (!is_wp_error($id)) {
            require_once ABSPATH . 'wp-admin/includes/image.php';
            $data = wp_generate_attachment_metadata($id, $file);
            wp_update_attachment_metadata($id, $data);
        }
        return $id;
    }