其中 error_page 502 = @apache; 是关键！！！

 location ~ .*\.php$
{
        error_page 502 = @apache;
        fastcgi_pass  127.0.0.1:9002;
        fastcgi_index index.php;
        fastcgi_param GATEWAY_INTERFACE CGI/1.1;
        fastcgi_param SERVER_SOFTWARE nginx;
        fastcgi_param QUERY_STRING $query_string;
        fastcgi_param REQUEST_METHOD $request_method;
        fastcgi_param CONTENT_TYPE $content_type;
        fastcgi_param CONTENT_LENGTH $content_length;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        fastcgi_param SCRIPT_NAME $fastcgi_script_name;
        fastcgi_param REQUEST_URI $request_uri;
        fastcgi_param DOCUMENT_URI $document_uri;
        fastcgi_param DOCUMENT_ROOT $document_root;
        fastcgi_param SERVER_PROTOCOL $server_protocol;
        fastcgi_param REMOTE_ADDR $remote_addr;
        fastcgi_param REMOTE_PORT $remote_port;
        fastcgi_param SERVER_ADDR $server_addr;
        fastcgi_param SERVER_PORT $server_port;
        fastcgi_param SERVER_NAME $server_name;
        # PHP only, required if PHP was built with --enable-force-cgi-redirect
        fastcgi_param REDIRECT_STATUS 200;
}

 location @apache {
        proxy_pass http://127.0.0.1:88;
        proxy_connect_timeout 30s;
        proxy_send_timeout   90;
        proxy_read_timeout   90;
        proxy_buffer_size    32k;
        proxy_buffers     4 32k;
        proxy_busy_buffers_size 64k;
        proxy_redirect     off;
        proxy_hide_header  Vary;
        proxy_set_header   Accept-Encoding '';
        proxy_set_header   Host   $host;
        proxy_set_header   Referer $http_referer;
        proxy_set_header   Cookie $http_cookie;
        proxy_set_header   X-Real-IP  $remote_addr;
        proxy_set_header   X-Forwarded-For $proxy_add_x_forwarded_for;
}