How to add to html <a> tag onclick event with PHP and call the function in JavaScript file

Question

This question maybe is little bit strange but I need to learn it asap.

I have a HTML file which is called upgrade.view.php here is the piece of code that I am on working on:

    <form role="form" method="get" action='index.php?action=Frontend_upgradeChosen'>
        <div class="col-md-5">
            <ul name="S_PRODUCT" id="S_VARIABLE">

            <?php                 
                 if (isset($oldProduct) && isset($arrayUpgrade)){
                     foreach ($arrayUpgrade as $value) {
                         $pro = $value->getnewProduct(); //                           
                    echo '<li><a href="index.php?action=Frontend_upgradeChosen" onclick="searchSN(this); return false;">'.$pro->getName().'</a></li>';                              
                }
            ?>   

            </ul>

        </div>
    </form>
    </div>

//which closes the main DIV

    <script type="text/javascript" language="javascript" src="<?= PATH_VIEWS_INCLUDES_URL ?>js/upgrade/upgrade.js"></script> 

On the other hand I am trying to call the JS function from upgrade.js where I have this function:

 function searchSN(elem) {        
        var a = elem.innerHTML;
        alert(a);

    }

Finally in my separated PHP file I have this function:

     public function upgradeChosen() {
                $selectedVariable = $_GET['S_PRODUCT'];
                echo 'The Price is:'." ". $selectedVariable;   
                include $this->getPrintedView();    
            }

As updated version of the question I am getting the on click event from the <A> tag but not the value the value of says undefined value.

I have updated the question so that maybe it makes it more understandable what I am trying to achieve.

Many Thanks in Advance

Answer 1

something like this ?

 function searchSN(elem) { var a = elem.innerHTML; alert(a); } 

 <form class="" role="form" method="get" action='index.php?action=Frontend_upgradeChosen'> <div class="col-md-5"> <ul name="S_PRODUCT" id="S_VARIABLE" > <li><a href="index.php?action=Frontend_upgradeChosen" onclick="searchSN(this); return false;">test</a></li> </ul> <button id='choose_product' type="submit" class='btn btn-default'><i class='icon-rocket'>Submit</i></button> </div> </form>