wp_media_upload_handler

		$html       = isset( $attachment['post_title'] ) ? $attachment['post_title'] : '';

		if ( ! empty( $attachment['url'] ) ) {
			$rel = '';

			if ( strpos( $attachment['url'], 'attachment_id' ) || get_attachment_link( $send_id ) == $attachment['url'] ) {
				$rel = " rel='attachment wp-att-" . esc_attr( $send_id ) . "'";
			}

			$html = "<a href='{$attachment['url']}'$rel>$html</a>";
		}

		/**
		 * Filters the HTML markup for a media item sent to the editor.
		 *
		 * @since 2.5.0
		 *
		 * @see wp_get_attachment_metadata()
		 *
		 * @param string $html       HTML markup for a media item sent to the editor.
		 * @param int    $send_id    The first key from the $_POST['send'] data.
		 * @param array  $attachment Array of attachment metadata.
		 */
		$html = apply_filters( 'media_send_to_editor', $html, $send_id, $attachment );

		return media_send_to_editor( $html );
	}

	return $errors;
}

/**
 * Handles the process of uploading media.
 *
 * @since 2.5.0
 *
 * @return null|string
 */
function wp_media_upload_handler() {
	$errors = array();
	$id     = 0;

	if ( isset( $_POST['html-upload'] ) && ! empty( $_FILES ) ) {
		check_admin_referer( 'media-form' );
		// Upload File button was clicked.
		$id = media_handle_upload( 'async-upload', $_REQUEST['post_id'] );
		unset( $_FILES );

		if ( is_wp_error( $id ) ) {
			$errors['upload_error'] = $id;
			$id                     = false;
		}
	}

	if ( ! empty( $_POST['insertonlybutton'] ) ) {
		$src = $_POST['src'];

		if ( ! empty( $src ) && ! strpos( $src, '://' ) ) {
			$src = "http://$src";
		}

		if ( isset( $_POST['media_type'] ) && 'image' !== $_POST['media_type'] ) {
			$title = esc_html( wp_unslash( $_POST['title'] ) );
			if ( empty( $title ) ) {
				$title = esc_html( wp_basename( $src ) );
			}

			if ( $title && $src ) {
				$html = "<a href='" . esc_url( $src ) . "'>$title</a>";
			}

			$type = 'file';
			$ext  = preg_replace( '/^.+?\.([^.]+)$/', '$1', $src );

			if ( $ext ) {
				$ext_type = wp_ext2type( $ext );
				if ( 'audio' === $ext_type || 'video' === $ext_type ) {
					$type = $ext_type;
				}
			}

			/**
			 * Filters the URL sent to the editor for a specific media type.
			 *
			 * The dynamic portion of the hook name, `$type`, refers to the type
			 * of media being sent.
			 *
			 * @since 3.3.0
			 *
			 * @param string $html  HTML markup sent to the editor.
			 * @param string $src   Media source URL.
			 * @param string $title Media title.
			 */
			$html = apply_filters( "{$type}_send_to_editor_url", $html, esc_url_raw( $src ), $title );
		} else {
			$align = '';
			$alt   = esc_attr( wp_unslash( $_POST['alt'] ) );

			if ( isset( $_POST['align'] ) ) {
				$align = esc_attr( wp_unslash( $_POST['align'] ) );
				$class = " class='align$align'";
			}

			if ( ! empty( $src ) ) {