php中获取真实IP地址与IP地址验证函数

function get_client_ip( )
{
        if ( getenv( "REMOTE_ADDR" ) && strcasecmp( getenv( "REMOTE_ADDR" ), "unknown" ) )
        {
                $onlineip = getenv( "REMOTE_ADDR" );
                return $onlineip;
        }
        if ( isset( $_SERVER['REMOTE_ADDR'] ) && $_SERVER['REMOTE_ADDR'] && strcasecmp( $_SERVER['REMOTE_ADDR'], "unknown" ) )
        {
                $onlineip = $_SERVER['REMOTE_ADDR'];
                return $onlineip;
        }
        if ( getenv( "HTTP_CLIENT_IP" ) && strcasecmp( getenv( "HTTP_CLIENT_IP" ), "unknown" ) )
        {
                $onlineip = getenv( "HTTP_CLIENT_IP" );
                return $onlineip;
        }
        if ( getenv( "HTTP_X_FORWARDED_FOR" ) && strcasecmp( getenv( "HTTP_X_FORWARDED_FOR" ), "unknown" ) )
        {
                $onlineip = getenv( "HTTP_X_FORWARDED_FOR" );
        }
        return $onlineip;
}

function is_ip( $IP )
{
        $IP_ARRAY = explode( ".", $IP );
        $IP_ARRAY_NUM = sizeof( $IP_ARRAY );
        if ( $IP_ARRAY_NUM != 4 )
        {
                return FALSE;
        }
        $I = 0;
        for ( ;    $I < $IP_ARRAY_NUM;    ++$I    )
        {
                if ( !is_numeric( $IP_ARRAY[$I] ) && $IP_ARRAY[$I] < 0 || 255 < $IP_ARRAY[$I] )
                {
                        return FALSE;
                }
                if ( !( $I == 3 ) && !( $IP_ARRAY[$I] == 255 ) )
                {
                        continue;
                }
                return FALSE;
        }
        return TRUE;
}