PHP获取公网IP地址的程序代码

/**
     * 获取真实IP地址
     */
    function get_real_ip(){
        if ( getenv( "HTTP_CLIENT_IP" ) && strcasecmp( getenv( "HTTP_CLIENT_IP" ), "unknown" ) ){
            $ip = getenv( "HTTP_CLIENT_IP" );
        }else if ( getenv( "HTTP_X_FORWARDED_FOR" ) && strcasecmp( getenv( "HTTP_X_FORWARDED_FOR" ), "unknown" ) ){
            $ip = getenv( "HTTP_X_FORWARDED_FOR" );
        }else if (getenv( "REMOTE_ADDR" ) && strcasecmp( getenv( "REMOTE_ADDR" ), "unknown" ) ){
            $ip = getenv( "REMOTE_ADDR" );
        }else if ( isset( $_SERVER[ 'REMOTE_ADDR' ] ) && $_SERVER[ 'REMOTE_ADDR' ]
            && strcasecmp( $_SERVER[ 'REMOTE_ADDR' ], "unknown" ) ){
            $ip = $_SERVER[ 'REMOTE_ADDR' ];
        }else{
            $ip = "unknown";
        }
        if ( strpos( $ip, ',' ) ){
            $ipArr = explode( ',', $ip );
            $ip = $ipArr[ 0 ];
        }
        return $ip;
}