Returns true if the IP Address passed in could have been mistakenly flagged as in the reserved range by FILTER_FLAG_NO_RES_RANGE

php_bug_66229_check.php

<?php
/**
 * Returns true if the IP Address passed in could have been mistakenly
 * flagged as in the reserved range by FILTER_FLAG_NO_RES_RANGE
 *
 * @see https://bugs.php.net/bug.php?id=66229
 * @see https://github.com/php/php-src/commit/d1314893fd1325ca6aa0831101896e31135a2658
 * @param $ip string An IP Address
 * @return bool
 */
function php_bug_66229_check( $ip ) {
	if ( ! filter_var( $ip, FILTER_VALIDATE_IP ) ) {
		return false;
	}

	$ip_arr = array_map( 'intval', explode( '.', $ip ) );

	if ( 128 == $ip_arr[0] && 0 == $ip_arr[1] ) {
		return true;
	}

	if ( 191 == $ip_arr[0] && 255 == $ip_arr[1] ) {
		return true;
	}

	return false;
}