taking down the system

I have a cron job that I will run every Sat night. 

One of the first things it does is:

$_SERVER['MAINT']=1;  

This creates a $_Server variable and sets it to one. At the end of the cron job I use:

$_SERVER['MAINT']=0;
echo('done with cron_job');
exit(0);

This correctly sets the MAINT to zero and exits.

But when a user brings up my main application, in the index() I have:

if ($_SERVER['MAINT']==1) {
   show_error("The Substantiator is down for weekly maintanance. ",500,"System down");
   exit(0);
}

This is not working. When I stop with the debugger on the line above and look for $_Server['MAINT']==1, it doesn't exist. This causes a real error instead of the fake one I am trying to create. 

I thought the $_SERVER variable is global on the Apache. What am I doing wrong?

Rich

proof that an old dog can learn new tricks