A simple PHP IPv4 regex checker, including an optional solution

regex.php

/**
 * @param $str the string to check
 * @return bool whether the String $str is a valid ip or not
 */
function isValidIP($str)
{
    /**
     * Alternative solution using filter_var
     *
     * return (bool)filter_var($str, FILTER_VALIDATE_IP);
     */

    /**
     * Normally preg_match returns "1" when there is a match between the pattern and the provided $str.
     * By casting it to (bool), we ensure that our result is a boolean.
     * This regex should validate every IPv4 addresses, which is no local adress (e.g. 127.0.0.1 or 192.168.2.1).
     * This pattern was debugged using https://regex101.com/
     */
    return (bool)preg_match('^(?:25[0-5]|2[0-4]\d|1\d\d|[1-9]\d|\d)(?:[.](?:25[0-5]|2[0-4]\d|1\d\d|[1-9]\d|\d)){3}$', $str);
}

please add a slash before ^ and before $, otherwise you'll have
"Warning: preg_match(): No ending delimiter '^' found in isValidIP("

Thus, this is working for me today

return (bool)preg_match('^(/?:25[0-5]|2[0-4]\d|1\d\d|[1-9]\d|\d)(?:[.](?:25[0-5]|2[0-4]\d|1\d\d|[1-9]\d|\d)){3}$/', $str);

    $this->data['ipv4'] = ( filter_var( $this->data['ip'], FILTER_VALIDATE_IP,FILTER_FLAG_IPV4) ) ? 1 : 0;
    $this->data['ipv6'] = ( filter_var( $this->data['ip'], FILTER_VALIDATE_IP,FILTER_FLAG_IPV6) ) ? 1 : 0;