WordPress at a glance
function is not described

valid_unicode() WP 2.7.0

Determines if a Unicode codepoint is valid.

No Hooks.

Return

true/false. Whether or not the codepoint is a valid Unicode codepoint.

Usage

valid_unicode( $i );
$i(int) (required)
Unicode codepoint.

Changelog

Since 2.7.0 Introduced.

Code of valid unicode: wp-includes/kses.php WP 5.2.2

<?php
function valid_unicode( $i ) {
	return ( $i == 0x9 || $i == 0xa || $i == 0xd ||
			( $i >= 0x20 && $i <= 0xd7ff ) ||
			( $i >= 0xe000 && $i <= 0xfffd ) ||
			( $i >= 0x10000 && $i <= 0x10ffff ) );
}