GD and Image Processing   [top]
GD is an open source code library for the dynamic creation of images by programmers. GD is written in C, and "wrappers" are available for Perl, PHP and other languages. GD creates PNG, JPEG and GIF images, among other formats. Most stock installations of PHP come with GD library support enabled.

Let's consider the following two examples. In both of them, we will use the GD library to create an image with a random text string (think "captcha" security codes for site login) using the following code:

# Create a random six letter alpha-numeric string
$string_a = array("A","B","C","D","E","F","G","H","J","K",
  "L","M","N","P","R","S","T","U","V","W","X","Y","Z",
  "2","3","4","5","6","7","8","9");
$keys = array_rand($string_a, 6);
foreach ($keys as $name=>$value)
{ $string .= $string_a[$value];
}

# Define background image URL
$bgimage = "images/background.gif";

$image = imagecreatefromgif($bgimage);
$color = imagecolorallocate($image, 0, 0, 0); # Create the color black

# Add the text
imagestring($image, 4, 15, 15, $string, $color);

$outfile = "images/random.gif";
imagegif($image,$outfile);

echo <<<END

Here is a PHP-generated image with random text:
<p>
<IMG SRC="$outfile" border="1">

END;

In our second example, the image data is actually sent straight to the browser

# Output the image
header("Content-type: image/gif");
imagegif($image);

Here is a PHP-generated image with random text:
<p>
<IMG SRC="gd-image.php" border="1">

For resizing, you first choose the method of how you want to resize - either to a set width and height, or to a percentage. You then call imagecopyresized() and output the data to a file. Because of security, newly created image files will have permissions set to 600, which means they can't be seen in a webpage. Invoking chmod() to change this to permissions 644 will fix this:

# Image names
$filename = "images/original.jpg";
$outfilegif = "images/thumb.gif";
$outfilejpg = "images/thumb.jpg";

$filetype = "";
if (preg_match("/\.(jpeg|jpg)$/i", $filename)) $filetype = "jpg";
if (preg_match("/\.(gif)$/i", $filename)) $filetype = "gif";

# Get new sizes
list($width, $height) = getimagesize($filename);

# set as a percentage
$percent = 0.5;
$newwidth = $width * $percent;
$newheight = $height * $percent;

# or set explicitly
$newwidth = 80;
$newheight = 80;

# create the thumb image
$thumb = imagecreatetruecolor($newwidth, $newheight);

# get the source data
if ($filetype=="gif")
{
  $source = imagecreatefromgif($filename);
  $outfile = $outfilegif;
}
elseif ($filetype=="jpg")
{
  $source = imagecreatefromjpeg($filename);
  $outfile = $outfilejpg;
}

# resize
imagecopyresized($thumb, $source, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);

# create the thumb
if ($filetype=="gif")
  imagegif($thumb,$outfile);
elseif ($filetype=="jpg")
  imagejpeg($thumb,$outfile);

# Change permissions on the new file - needed for proper web display
#  default of newly created file is 600 - need it to be 644
chmod($outfile, 0644);

All of these examples are served over the web, but they just as easily could have been created via the command-line interface and scheduled via cron. If users are uploading lots of images, and you wish to have thumbnails of these assets, you could scehdule a script to run every 5 minutes that resizes any newly uploaded images and deposits the output in a thumbnail directory.

Intro to Regular Expressions   [top]
One of the most powerful tools for matching and manipulating text is the regular expression (regex). In short, it's the ability to match specific patterns in text, and then perform tasks based upon how these patterns match strings of interest. For example, if we look at a US phone number:

212-555-1212

212-5551-212

1-212-555-1212

Regular expressions come in a few different flavors, with the most popular based upon the syntax of Perl:

For reference, the atoms of pattern matching in Perl are:

Metacharacters
^   Match the beginning of the line
.   Match any character (except newline)
$   Match the end of the line (or before newline at the end)
|   Alternation
()  Grouping
[]  Character class

Useful Patterns
\w  Match a "word" character (alphanumeric plus "_")
\W  Match a non-word character
\s  Match a whitespace character
\S  Match a non-whitespace character
\d  Match a digit character
\D  Match a non-digit character

Quantifiers
*      Match 0 or more times
+      Match 1 or more times
?      Match 1 or 0 times
{n }    Match exactly n times
{n,}   Match at least n times
{n,m}  Match at least n but not more than m times

You can test these out using these interactive regular expression tools for PHP below. Note that they are password-protected. Please use your regular Stage login to access:

For some more background on regular expressions, here's what the WikiPedia has to say, along with a set of bookmarks for further study:

Using HTTP in PHP   [top]
In the same way you used the mail() function to interface to SMTP to send e-mail, you can use HTTP to get the contents of a web page into a string in PHP. The Client URL (Curl) library excels at this:

$urlToGet = 'http://www.yahoo.com';

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $urlToGet);

# This option causes the curl_exec function to return response as a string
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);

# Use the following if you need to submit a FORM
# curl_setopt ($ch, CURLOPT_POST, 1);
# curl_setopt ($ch, CURLOPT_POSTFIELDS, "zip=10003");
 
$rawText = curl_exec($ch);
curl_close($ch);

$statusMsg = "Successfully obtained: $urlToGet";

<a : indicates that a link is present
href=" : indicates start of a link
"> : indicates end of a link and start of the linked text
</a> : indicates end of the linked text

$parts = array();
$pattern = '/<a .*?href="(.*?)".*?>(.*?)<\/a>/s';
preg_match_all($pattern,$rawText,$parts);

# $parts[0] now contains the entire part of the text that matched the expression
# $parts[1] now contains the URLs that matched between href="(.*?)"
# $parts[2] now contains the linked text that matched between >(.*?)<\/a>

# Uncomment this is you want to view the entire result array
# print_r($parts);

# htmlspecialchars() subs the HTML equiv for certain chars, i.e. & for &
for($i=0; $i<count($parts[1]); $i++)
{ $parts[1][$i] = trim($parts[1][$i]);
  $parts[2][$i] = trim($parts[2][$i]);
  print "<li>".htmlspecialchars($parts[1][$i])." - ".htmlspecialchars($parts[2][$i])."\n";
}

Object Oriented Design   [top]
When talking about object oriented design in the context of software, one is usually referring to a class-based system of grouping functionality to achieve a simplicity in the organization and maintenance of your code. As we've seen from some of the previous procedural examples, things can become a bit unruly very quickly.

In the PHP realm, classes essentially consist of properties and methods:

class Pizza
{
  # in seconds
  private $bake_times = array(
    'cheese' => 480,
    'sicilian' => 720,
    'veggie' => 600,
  );
  
  public function getBakeTime($type)
  {
    $time = $this->bake_times[$type];
    return $time;
  }
}

$my_pizza = new Pizza;
$time_to_cook = $my_pizza->getBakeTime('veggie');

Web Application Frameworks and the MVC Model   [top]
In the real world, a lot of the heavy lifting in serving a larger website is done for you by web frameworks, which are object-oriented in nature. Usually, a web framework is an integrated library of code that provides methods and resources for common tasks used in creating and serving a web application such as:

• Database Interaction
• Form & User Input Validation
• Templating
• Authentication and Authorization
• Session Management
• URL Management
• Caching
• Javascript Integration

The Favorite Sites Demo as faux MVC Model   [top]
To illustrate this concept, we can recast our favorite sites demo using the MVC metaphor.

Favorite Sites Demo using faux MVC Model

In order to restrucure this, we'll use a few different files:

• index.php - this will be our controller and serve all pages for the demo
• model.php - this will hold the PHP class that handles all our database activity
• view_list.php - holds the display template to show a list of sites
• view_list_text.php - text-based version of site list
• view_add.php - holds the display template to show a list of sites
• view_header.php - initial part of HTML template
• view_footer.php - ending part of HTML template

$site_defs = array(
  'db' => array(
    'host'=>'localhost',
    'database'=>'net_id',
    'un'=>'net_id',
    'pw'=>'mysql_pw',
  ),
);

public function getConnection()
{
  require "info.php";
  
  $connection = mysql_connect($site_defs['db']['host'], $site_defs['db']['un'], $site_defs['db']['pw']);
  if (!$connection) return;

  $db_selected = mysql_select_db($site_defs['db']['database'], $connection);
  if (!$db_selected) return;
  
  return $connection;
}


public function closeConnection($connection)
{
  mysql_close($connection);
}


public function getSites()
{
  $conn = $this->getConnection();
  if (!$conn) return;
  
  $sql = "SELECT s.id as site_id, s.title, s.url, s.description,
s.votes, c.id as cat_id, c.name as cat_name
FROM class05_table2 s, class05_category c
WHERE s.category_id=c.id
ORDER BY s.votes desc, s.title";
  $result = mysql_query($sql,$conn);
  if (!$result) return;
  while(($rows[] = mysql_fetch_assoc($result)) || array_pop($rows));
  
  # Augment the data with the category name
  $data = array();
  foreach($rows as $row):
    if ($row['cat_id']<=1) unset($row['cat_name']);
    $data[] = $row;
  endforeach;
  
  return $data;
}

Introduction to Codeigniter   [top]
CodeIgniter is a powerful PHP framework with a very small footprint, built for PHP coders who need a simple and elegant toolkit to create full-featured web applications. CodeIgniter is an Application Development Framework - a toolkit - for people who build web sites using PHP. Its goal is to enable you to develop projects much faster than you could if you were writing code from scratch, by providing a rich set of libraries for commonly needed tasks, as well as a simple interface and logical structure to access these libraries. CodeIgniter lets you creatively focus on your project by minimizing the amount of code needed for a given task.

• CodeIgniter Home Page
• Video Tutorials
• User Guide
• Database documentation
• Favorite Sites Demo in Codeigniter
• Sample Model
• Sample View
• Sample Controller

Related Resources   [top]