onclick event on hyperlink being performed prematurely

Question

I want to be able to select a favorite product from a shopping cart. This is my code (it is from IBKCart modified):

<?php
    function ShowCartWtPrd(){
        global $fav_id;
        $itemClass = ($this->getCartItems() > 2) ? "insideContMainArea2": "insideContMainArea";
        $plural = ($this->getCartItems() > 1)? 's': '' ;


        if (isset($_SESSION['favourites']) && !$_SESSION['favourites'] == "False") {

            $this->updFavourites();
            unset($_SESSION['favourites']);
        }                        

        $Out = 
        '<div id="theOverlay">&nbsp; 
          <table width="100%" border="0" cellspacing="0" cellpadding="2">
            <tr>
              <td width="20%"><div align="right"><img name="" src="./imgs/wait.gif" width="32" height="32" alt="" /></div></td>
              <td width="50%"><div align="left">&nbsp;<strong>Updating...Please Wait</strong> </div></td>
            </tr>
          </table>
        </div>
        <div id="Cart_Container">
            <div id="Car_top_bg"></div>
          <div id="Cart_middle">
                 <div id="'. $itemClass. '">
                   <table width="100%" border="0" cellspacing="2" cellpadding="2">
                     <tr bgcolor="#E6EDD2">
                       <td width="55%" height="21" bgcolor="#E6EDD2"><div align="center"><strong>Item Description </strong>
                       </div>
                       </td>
                       <td width="11%"><div align="center"><strong>Qty</strong></div></td>
                       <td width="11%"><div align="center"><strong>Prc/Qty</strong></div></td>
                       <td width="11%"><div align="center"><strong>Fav</strong></div></td>
                       <td width="11%"><div align="center"><strong>Del</strong></div></td>
                     </tr>' ;
                     $cnt=1;
                     foreach($this->cart as $itemId=>$Qty){
                        ++$cnt;
                        $ans = fmod($cnt,2);
                        if($ans == 0){$bg = '#ECF9FF';}else{$bg='';};
                        $ProdDts = $this->getProdDts($itemId);

                        $this->totAmt += $ProdDts[$this->prodPrc] * $Qty ;
                        $fav_id = $ProdDts[$this->prod_id];

                            $Out .= '<tr bgcolor="'. $bg .'">
                            <td valign="top">
                                <table width="100%" border="0" cellspacing="1" cellpadding="0">
                                 <tr>
                                    <td width="60%" valign="top">
                                        ' . $ProdDts[$this->prodNm]  .' 
                                        <br />                   
                                    </td>
                                 </tr>
                                </table>
                               </td>
                               <td valign="top"><div align="center">' . $Qty .'</div></td>
                               <td valign="top">' . $ProdDts[$this->prodPrc]  .'</td>
                               <td valign="top">
                                    <div align="center">
                                        <a href="#?favourites=true">
                                            <img src="./imgs/fav_trnsp_icon.png" 
                                                alt="Add to favourites" width="16" height="16" border="0" 
                                                title="Add to favourites" name="favourites"
                                                onclick="document.write('. $this->updFavourites() .');"
                                            />                                                                         
                                        </a>
                                    </div>
                                </td>
                               <td valign="top">
                                    <div align="center">
                                        <a href="#" 
                                            onclick="doCart(\'DelItem\', \'' . $ProdDts[$this->prodId] . '\', 0, \' \', \'Small\');">
                                            <img src="./imgs/cart_remove.png" alt="Delete Item" width="16" height="16" border="0" title="Delete Item"/></a>
                                    </div>
                                                               </td>
                             </tr>
                             <tr>
                       <td colspan="4" valign="top"><div class="clear"></div></td>
                     </tr>';
                     }

                    $Out .= '
                   </table> 
                 </div>
          </div>
            <div id="Cart_gtotal">
                <div class="theCont">Grand Total => '. $this->ShowCurSymbol() .' '. $this->toMoney($this->totAmt) . '</div>
            </div>
        </div>' ;   

        echo $Out;
    }
            function updFavourites() {
                global $username;
                global $password;
                global $database;
                global $fav_id;
                $conn = mysqli_connect("localhost",$username,$password, $database);
                // Check connection
                if (mysqli_connect_errno($conn))
                  {
                  echo "Failed to connect to MySQL: " . mysqli_connect_error();
                  }
                // mysql_connect("localhost","$username","$password") or die("Error: ".mysqlerror());
                // mysql_select_db("$database");
                if (isset($_SESSION['fav_id'])) {
                    $fav_id = $_SESSION['fav_id'];
                }
                $dealer_id  = $_SESSION['dealer_id'];
                $ProdDts = $this->getProdDts($fav_id);

                $part_id        = $ProdDts[$this->prod_id];
                $sql = "INSERT INTO favourites VALUES (0,'$dealer_id','$part_id')";
                $result = $conn->query($sql) or exit("Error code ({$conn->errno}): {$conn->error}");

                /* close up */
                //$conn->close();
            }
 ?>

            }

If I step through the code with a debugger, I get as far as the line

$Out .= '<tr bgcolor="'. $bg .'">

and it goes straight into the updFavourites() function, Which I wanted to do on the onclick event "favourites" near the end of the ShowCartWtPrd function. I have been trying to debug this but can't see what is causing it. Perhaps someone has an idea.

You have not understood the difference between server-side PHP code and client-side JavaScript code yet … _of course_ `updFavourites` gets executed there and then, because it is a PHP function. PHP is long done with its work, _before_ the page even reaches the client. — CBroe, Apr 03 '14 at 20:24
as I said to Bikonja, the `updFavourites` is dependent on the session variable `favourites` which only gets set by the onclick evernt, so I can't see how that happens. — Geoff, Apr 03 '14 at 23:15

score 1 · Answer 1 · answered Apr 03 '14 at 20:26

1

You are confusing server-side and client side events. The onclick event you are using is a javascript (client-side) event and will be executed when the user clicks on the element, but since you are outputting the string $Out from PHP (server-side) and you are concatenating the values of the string constants and the updFavourites function, PHP executes the server-side code and then gives the client-side code which is the evaluated PHP function.

answered Apr 03 '14 at 20:26

Bikonja

909
5
15

I certainly get what you are saying, but why does the function `updFavourites()`get called. There is only one call to it in the code and that seems to be dependent on the onclick event. Is that explicable? – Geoff Apr 03 '14 at 23:12
@Geoff It shouldn't be dependent on the onclick event. The PHP variable to which you concatenate the `updFavourites` function is always called within an iteration of the `foreach` loop. Are you maybe not entering the `foreach`? PHP doesn't event know what `onclick` is so it's not dependant on that. Try seeing if the `foreach` is being called when you think the `onclick` is not "triggered". – Bikonja Apr 04 '14 at 07:41
I got the code for this onclick event from this question: [link](http://stackoverflow.com/questions/7451070/calling-a-php-function-by-onclick-event). ** The onClick attribute of html tags only takes Javascript but not PHP code. However, you can easily call a PHP function from within the Javascript code by using by using the JS document.write() function - effectively calls the PHP function by "writing" its call to the browser window** – Geoff Apr 04 '14 at 08:54
That answer is badly written. Using `document.write('');` is just so you could add **evaluated** PHP code to your page `onclick`, so while it does defer writing to your HTML page to the `onclick` event, it does not defer the PHP evaulation of the code that it will put in the `document.write` part. The only way to call a PHP function from a javascript `onclick` is by using AJAX. – Bikonja Apr 04 '14 at 12:54

onclick event on hyperlink being performed prematurely

1 Answers1