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; 
}