upload_is_file_too_big( array $upload )

Source

File: wp-includes/ms-functions.php

function upload_is_file_too_big( $upload ) {
	if ( ! is_array( $upload ) || defined( 'WP_IMPORTING' ) || get_site_option( 'upload_space_check_disabled' ) ) {
		return $upload;
	}

	if ( strlen( $upload['bits'] ) > ( KB_IN_BYTES * get_site_option( 'fileupload_maxk', 1500 ) ) ) {
		/* translators: %s: Maximum allowed file size in kilobytes. */
		return sprintf( __( 'This file is too big. Files must be less than %s KB in size.' ) . '<br />', get_site_option( 'fileupload_maxk', 1500 ) );
	}

	return $upload;
}