Use of different Method from Controller on Button in HTML - php

Question

crew,
I have a controller_jobs.php in which I have two methods. The index method in which every job from my database that is available is pulled from the DB and assigned to my template, career.html. In the career.html I display every available job through a foreach, this works as intended.
The second method is called show and is called with the primary key from the job.
In my html I got a Button at every job position. The HTML was designed from another company and is still hardcoded with an href call to the second template career-details.html.
How can I manage to call the show() function from the controller on this button and start the next template??
<div class="wu__ltblue--bg eq row--flex row--aic row--jcc">
<a href="career-details.html" class="btn btn-borderd">
<span class="fa-stack">
<i class="fa fa-circle fa-stack-2x icon-background1"></i>
<i class="fa fa-chevron-right fa-stack-1x"></i>
</span> Ansehen</a>
</div>
I was told to use a form to call the method in there, but I'm not certain about how to use it.
Thanks for help in advance.
The example I got was to lookup on things they already did.
<form id="form_reserve" method="post" action="{$SITEURL}payprocess&PHPSESSID={$SID}"> "Buttoncode" </form>
To be honest, i don't understand what they did in there as I am pretty new to webdevelopment.
And these are my functions from the controller.php
public function index() {
$js_array = array();
$jobs = array();
$dbJobs = new DBJobs();
$jobs = $dbJobs->getAll();
$ControllerLibs = new ControllerLibs();
foreach ($jobs as &$job) {
$job['STELLENKURZBESCHREIBUNG'] = $job['STELLENKURZBESCHREIBUNG'];
$job['STELLENBESCHREIBUNG'] = $job['STELLENBESCHREIBUNG'];
$job['PDFDOKUMENT'] = $job['PDFDOKUMENT'];
$job['BILD'] = $job['BILD'];
$job['PK'] = $job['PK'];
$template = $this->template;
$template->assign('JS_FILES', $js_array);
$template->assign('JOBS', $jobs);
$template->display('career.html');
} // Index
public function show($pk) {
$js_array = array();
$jobs = array();
$dbJobs = new DBJobs();
$jobs = $dbJobs->getByPK($pk);
foreach ($jobs as &$job) {
$job['STELLENKURZBESCHREIBUNG'] = $job['STELLENKURZBESCHREIBUNG'];
$job['STELLENBESCHREIBUNG'] = $job['STELLENBESCHREIBUNG'];
$job['PDFDOKUMENT'] = $job['PDFDOKUMENT'];
$job['BILD'] = $job['BILD'];
}
}