Remove Unnecessary Code by Rethinking Your Default Setting

Over the past few years, I've spent a lot of time revamping my old code. I've been doing what I can to simplify, simply, simplify. While going through the code, I started noticing a pattern when it came to setting defaults. Let's take a look at a quick example and see how I was able to remove the unnecessary code.

Background

One page that I found displays staff presentations from a MySQL table like the following:

When you initially visit the page, it displays a list of presentation titles. Clicking on any of those titles brings you to the same page, but the page now shows the details associated with the presentation. Here is a simplified version of what the code looked like:

<?php
//CONNECT WITH ONLINE DATABASE
require "{$_SERVER['DOCUMENT_ROOT']}/../connect.html";
 
//INITIALIZE VARIABLES
$presentations = array();
$showList      = false;
$showDetails   = false;
 
//GET PRESENTATION LIST
$sql = "SELECT id, title FROM presentations ORDER BY date DESC";
if($result = $mysqli->query($sql)) {
     while($row = $result->fetch_assoc()) {
          $presentations[$row['id']] = $row['title'];
     }
}
 
//IF SHOWING A PRESENTATION
if(isset($_GET['show'])) {
     //IF PASSED ID IS VALID
     if(in_array($_GET['show'], array_keys($presentations))) {
          //GET PRESENTATION
          $sql = "SELECT title, presenter, date, location FROM presentations WHERE id={$_GET['show']} LIMIT 1";
          if($result = $mysqli->query($sql)) {
               if($row = $result->fetch_assoc()) {
                    $showDetails = true;
 
               //ELSE...PRESENTATION ENTRY NOT FOUND
               } else {
                    $showList = true;
               }
 
          //ELSE...QUERY FAILED
          } else {
               $showList = true;
          }
 
     //ELSE...INVALID ID
     } else {
          $showList = true;
     }
 
//ELSE...SHOWING THE LIST
} else {
     $showList = true;
}
 
//IF SHOWING A PRESENTATION
if($showDetails) {
     print "<div>Title:     {$row['title']}</div>";
     print "<div>Presenter: {$row['presenter']}</div>";
     print "<div>Date:      {$row['date']}</div>";
     print "<div>Location:  {$row['location']}</div>";
 
//ELSE...IF SHOWING THE LIST
} elseif($showList) {
     print '<ul>';
     foreach($presentations as $currID=>$currTitle) {
          print "<li><a href='?show=$currID'>$currTitle</a></li>";
     }
     print '</ul>';
}
?>

Change the Default

You may have noticed that $showList flag is set to true in quite a few spots. The code could be made a lot simpler by just changing the default value for $showList.

<?php
//CONNECT WITH ONLINE DATABASE
require "{$_SERVER['DOCUMENT_ROOT']}/../connect.html";
 
//INITIALIZE VARIABLES
$presentations = array();
$showList      = true;
$showDetails   = false;
 
//GET PRESENTATION LIST
$sql = "SELECT id, title FROM presentations ORDER BY date DESC";
if($result = $mysqli->query($sql)) {
     while($row = $result->fetch_assoc()) {
          $presentations[$row['id']] = $row['title'];
     }
}
 
//IF SHOWING A PRESENTATION
if(isset($_GET['show'])) {
     //IF PASSED ID IS VALID
     if(in_array($_GET['show'], array_keys($presentations))) {
          //GET PRESENTATION
          $sql = "SELECT title, presenter, date, location FROM presentations WHERE id={$_GET['show']} LIMIT 1";
          if($result = $mysqli->query($sql)) {
               if($row = $result->fetch_assoc()) {
                    $showDetails = true;
               }
          }
     }
}
 
//IF SHOWING A PRESENTATION
if($showDetails) {
     print "<div>Title:     {$row['title']}</div>";
     print "<div>Presenter: {$row['presenter']}</div>";
     print "<div>Date:      {$row['date']}</div>";
     print "<div>Location:  {$row['location']}</div>";
 
//ELSE...IF SHOWING THE LIST
} elseif($showList) {
     print '<ul>';
     foreach($presentations as $currID=>$currTitle) {
          print "<li><a href='?show=$currID'>$currTitle</a></li>";
     }
     print '</ul>';
}
?>

Use Else Instead

And in this particular case, the $showList flag could be removed altogether. Since we're always displaying the list of presentation titles unless one of the links is clicked, we could just use an else statement.

<?php
//CONNECT WITH ONLINE DATABASE
require "{$_SERVER['DOCUMENT_ROOT']}/../connect.html";
 
//INITIALIZE VARIABLES
$presentations = array();
$showDetails   = false;
 
//GET PRESENTATION LIST
$sql = "SELECT id, title FROM presentations ORDER BY date DESC";
if($result = $mysqli->query($sql)) {
     while($row = $result->fetch_assoc()) {
          $presentations[$row['id']] = $row['title'];
     }
}
 
//IF SHOWING A PRESENTATION
if(isset($_GET['show'])) {
     //IF PASSED ID IS VALID
     if(in_array($_GET['show'], array_keys($presentations))) {
          //GET PRESENTATION
          $sql = "SELECT title, presenter, date, location FROM presentations WHERE id={$_GET['show']} LIMIT 1";
          if($result = $mysqli->query($sql)) {
               if($row = $result->fetch_assoc()) {
                    $showDetails = true;
               }
          }
     }
}
 
//IF SHOWING A PRESENTATION
if($showDetails) {
     print "<div>Title:     {$row['title']}</div>";
     print "<div>Presenter: {$row['presenter']}</div>";
     print "<div>Date:      {$row['date']}</div>";
     print "<div>Location:  {$row['location']}</div>";
 
//ELSE...SHOW THE LIST
} else {
     print '<ul>';
     foreach($presentations as $currID=>$currTitle) {
          print "<li><a href='?show=$currID'>$currTitle</a></li>";
     }
     print '</ul>';
}
?>

Conclusion

While all three methods provide the same result, it can take a lot less code by just putting more thought into the default settings.