How is this working?

I'm trying to trace the logic of a page that's using Blitz.

The index.php has several functions at the top, but it's the bottom that I'm thinking represents the answer to my questions.

if (!empty($subDomain) && file_exists(REG_ROOT.'templates/'.$subDomain.'.tpl')) {
    
    if($_GET['resetSession']){
        resetSession();
    }
    
    $T = new Blitz(REG_ROOT.'templates/'.$subDomain.'.tpl');

    $_POST['subdomain'] = $subDomain;
    $out = array_merge($_GET, $_POST);

    if(!empty($_POST['verifyUser'])){
        if(verifyUser($_POST)){
            $out['usrVerified'] = 1;
            unset($_POST['findUser']);
        } else {
            unset($_POST['verifyUser'],$out['usrID']);
            $_POST['findUser'] = 1;
        }
    } 

    if(!empty($_POST['findUser'])){
        $usrArray = findUser($_POST);
        if(is_array($usrArray)){
            $out = array_merge($out,$usrArray);
        } else {
            $out['usrMsg'] = $usrArray;
        }
        echo $T->parse($out);
        return false;
    }
    
     if(!empty($_POST['findCoachingSessions']) && is_numeric($out['usrID'])){
        $out['event_list'] = findCoachingSessions($out['empID'], $out['usrID'], $subDomain);
        if(is_array($out['event_list'])){
            foreach($out['event_list'] as &$event){
                $event['guid'] = buildGUID(array('empID'=>$out['empID'],'evID'=> $event['evID'],'ruEvent'=>'email-click','ruReferrer'=>'ezor.net','ruVerb'=>'register','ruObj'=>'event','usrID'=>$out['usrID'], 'hID'=>$out['hID']));
            }
        } else {
            $out['usrMsg'] = $usrArray;
        }
        
        /*
        $out['appt_list'] = findAppointments($out['usrID']);
        if(is_array($out['appt_list'])){
            if(count($out['appt_list'])>0){
                foreach($out['appt_list'] as &$appt){
                    $appt['guid'] = buildGUID(array('empID'=>$out['empID'],'aID'=> $appt['aID'],'ruEvent'=>'email-click','ruReferrer'=>'ezor.net','ruVerb'=>'register','ruObj'=>'coaching','usrID'=>$out['usrID']));
                }
            } else {
                $out['appt_list'] = 0;
            }
        } else {
            $out['usrMsg'] .= $usrArray;
        }
        */
        echo $T->parse($out);
        return false;
    }
    
        $out['event_list'] = findEvents($out['empID']);
        $out['survey'] = findSurvey($out['empID']);
		if(empty($out['hID'])){
			$out['hID'] = $out['survey']['hID'];
		}

        if(is_array($out['event_list']) && sizeof($out['event_list'])>0){
            foreach($out['event_list'] as &$event){
                $event['guid'] = buildGUID(array('empID'=>$out['empID'],'evID'=> $event['evID'],'ruEvent'=>'email-click','ruReferrer'=>'cpap','ruVerb'=>'register','ruObj'=>'event','usrID'=>$out['usrID'], 'hID'=>$out['hID']));
            }
        } else {
            $out['event_list'] = array('guid'=>'resetSession=1','evName'=>'No schedule found for this location. Please click to choose another','url'=>$_SERVER['PHP_SELF'],'target'=>'_self');
        }
        $out['survey_guid'] = buildGUID(array('empSurveyUsername'=>$out['survey']['credUsername'], 'empSurveyPassword'=>decrypt($out['survey']['credPassIV'], $out['survey']['credPass']), usrLang=>'', 'empID'=>$out['empID'], 'hID'=>$out['hID'], 'usrID'=>$out['usrID']));
        
    } else {
        echo 'Error loading employer data.';
    }

    echo $T->parse($out);
}

Select allOpen in new window

Line 1, you've got an IF statement that's looking for a subDomain and if there's something present, we're moving forward.

Line 7, we instantiate a new Blitz dynamic,

Now, here's my question...

The HTML, at one point, has this:

 <<div class="row">
		<div class="col-xs-12">
		{{ IF $empID }}
        <h4>Step 1:</h4>
            {{IF $evName}}Selected site: {{$empName}}{{ELSE}} Site Selected.{{END}}
	       <h4>Step 2:</h4>
        <p>Select a class from the list to register for classes:</p>
        {{ BEGIN event_list }}
            {{ UNLESS $url }}
                <div><a href="https://personalhealthsurvey.net/event.php?{{$guid}}" target="{{IF $target}}{{$target}}{{ELSE}}_blank{{END IF}}">{{$evName}}</a></div>
            {{ ELSE }}
                <div><a href="{{$url}}?{{$guid}}" target="{{IF $target}}{{$target}}{{ELSE}}_blank{{END IF}}">{{$evName}}</a></div>
            {{ END IF }}
        {{ END event_list }}
                <p><br>
                    Once you have scheduled your screening, you can log in again to the scheduler to change or cancel your appointment. Confirmation emails will contain a link back to the online scheduler.
                </p>
            {{ ELSE }}
            <h4>Step 1:</h4>
               <form name="kickit" method="post" action="#">
					<input type="hidden" name="evID" id="evID" value="3851,3844,3842,3838,3830,3822,3781,3780,3848,3854,3847,3846,3845,3843,3841,3840,3837,3836,3825,3824,3823,3785,3784,3783,3782,3850,5068,5110" style="visibility:hidden">
                    <input type="hidden" name="fetchEvents" value="1" />
                    <select id="empID" name="empID" onchange="if (this.value.length > 0) kickit.submit();" class="form-control">
                        <option value="">Select a Site</option>
                    <!--I removed the actual hospital names-->
                   <option>hospital names>/option>
                    </select>
                </form>
                <p><br>
                    Once you have scheduled your screening, you can log in again to the scheduler to change or cancel your appointment. Confirmation emails will contain a link back to the online scheduler.
                </p>
			{{ END IF }}
			</div>
		</div>

Select allOpen in new window

You're submitting a form "onchange," but there's nothing on the index.php that's seemingly interested in either of the hidden fields, as far as what would trigger dynamic content.

There is, however, a Blitz IF statement asking for the presence of an $empID variable ({{ IF $empID }}).

Looking at the index.php page on line 61, you see this:

 if(empty($out['empID'])){

What is $out and is this line what I'm thinking it is, as far as the thing that determines what is viewed on the .tpl page?