Global variables with CGI:Ajax

me_gazza has asked for the wisdom of the Perl Monks concerning the following question:

Hello I have a funny (probably due to my lack of understanding of the inerds of Perl!) where I have set a global hash variable (using our), and then create some AJAX subroutines hash mappings to be exported to javascript (HTML page created via HTML::Template:Pro in the first instance). I have found that each "callback" does not persist the data to the global hash when printed in each subroutine.

Is there another way to maintain the returned values via AJAX for an HTML page with multi choice pre submission?

eg..(simple cut down for reference)

our %myhash;

my $cgi = CGI->new();

my %funchash = ( 'SUBA'    => \&suba,

                 'SUBB'    => \&subb );


my $pjx = CGI::Ajax->new( %funchash );


my $var1="aaa";

$myhash{typea}=$var1;


my $template="html/mypage.html";

my $tmpl= HTML::Template::Pro->new(filename => $template,loop_context_
+vars=>1,debug=>1,global_vars=>1);


print $pjx->build_html( $cgi, $tmpl->output)


sub suba {

# this is invoked by user clicking on dropdown box A

$myhash{typeb}="bbbb";

print "$myhash{typea}";  <- this is shown correctly 

print "$myhash{typeb}";  <-  this is shown correctly 

} 


sub subb { 

# this is invoked after user clicked dropdown box B after A 

$myhash{typec}="cccc"; 

print "$myhash{typea}";  <- this is shown correctly 

print "$myhash{typeb}";  <-  this is _NOT_ shown 
 print "$myhash{typec}";  <-  this is shown correctly 



}
[download]

Many Thanks
Gareth

Comment on Global variables with CGI:Ajax Download Code

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Re: Global variables with CGI:Ajax by Anonymous Monk on May 28, 2012 at 21:24 UTC
I have found that each "callback" does not persist the data to the global hash when printed in each subroutine. Yeah, in-memory-data does not persist between different processes, when the process ends, the data is gone To persist the data you would use a server-side-cache, like CGI::Session, Apache::Session, CHI ... Read more about memory management at Re^3: Scope of lexical variables in the main script	[reply]
Re^2: Global variables with CGI:Ajax by me_gazza (Initiate) on May 29, 2012 at 08:23 UTC
Thanks for the info. I just did a simple print FILE test using $$ on the name and can see as you say it is a different process each time. This implies the entire screen on the browser is refreshed for each AJAX call right? I thought AJAX (in my simple mind) was clever in that it simply modified the element (div) on screen and used the called script/function to provide the modification? I am wondering why I both using AJAX in that case and just let the entire HTML page refresh with some hidden variables to control what actions occur on the next call of the cgi object. Any thoughts on that? Many Thanks	[reply]
Re^3: Global variables with CGI:Ajax by Anonymous Monk on May 29, 2012 at 09:42 UTC
This implies the entire screen on the browser is refreshed for each AJAX call right? Nope, it implies each HTTP request AJAX makes is serviced by a different CGI program instance. Read more about this (watch the video too) at learn about the internet,Web Programming: For Beginners, to get an overall picture of how the internet works, how tcp/ip, sockets, html, ajax, all fit together.	[reply]