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";

$filetype = "";
if (eregi("[.](jpeg|jpg)$", $filename)) $filetype = "jpg";
if (eregi("[.](gif)$", $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
    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";
}

Using FTP in PHP   [top]
PHP has an included FTP extension that allows scripts to transfer files between the local server and a remote FTP host.

# Get our FTP account info (username, pw, remote FTP host)
require "info_ftp.php";

/*
# Info to define in info_ftp.php
$username = "[your FTP username]";
$password = "[your FTP password]";
$host = "ftp.domain.com";  # Change to name of remote FTP host
*/

$source_file = "test.pdf"; # local file to send to remote host
$destination_file = "test.pdf"; # name of this file on remote host

$remote_file = "test.pdf"; # remote file to transfer to local server
$local_file = "test_downloaded.pdf"; # name of this file on local server

$file_type = FTP_BINARY; # Constant known to PHP
# $file_type = FTP_TEXT; # Use this if transferring a text file


# Set up basic connection
$ftp = ftp_connect($host); 

# Login with username and password
$login_result = ftp_login($ftp, $username, $password); 

# Check connection
if ((!$ftp) || (!$login_result))
{ 
  print "FTP connection has failed!\n";
  print "Attempted to connect to $host for user $username\n"; 
  exit; 
}
else
{
  print "Connected to $host, for user $username\n";
}

# Turn passive mode on - needed if the script is running on a server behind a firewall
#  This means that the script will initiate the data connections, not the remote host
ftp_pasv($ftp, true);

# Get listing of the current directory and output
$contents = ftp_rawlist($ftp, ".");
print "\n--- Before ---\n";
foreach ($contents as $line) print "$line\n";
print "\n";

# Attempt to upload this file and check status
$upload_status = ftp_put($ftp, $destination_file, $source_file, $file_type); 
if (!$upload_status)
{ 
  print "FTP upload has failed!\n";
}
else
{
  print "Uploaded $source_file to $host as $destination_file\n";
}

# Get listing of the current directory and output
$contents = ftp_rawlist($ftp, ".");
print "\n--- After ---\n";
foreach ($contents as $line) print "$line\n";
print "\n";

# Attempt to download this file and check status
$download_status = ftp_get($ftp, $local_file, $remote_file, $file_type); 
if (!$upload_status)
{ 
  print "FTP download has failed!\n";
}
else
{
  print "Downloaded $remote_file from $host as $local_file\n";
}

# Close the FTP connection 
ftp_close($ftp);

Using IMAP in PHP   [top]
IMAP stands for Internet Message Access Protocol and is the one of the main methods for retrieving email from a remote server (along with POP3). PHP has an included IMAP extension that allows scripts to retrieve email messages via both IMAP and POP3. This means you can use PHP to get email from Gmail, NYU, or any other mail provider that allows remote access via IMAP or POP3.

# Get our email account info (email, pw, mail host connection string)
require "info_imap.php";

#########################################################
# Some possible connection options to define in info_imap.php
#########################################################
/*

# Non-secure POP3 - Change "mail.domain.com" to your POP3 server name
$username = "[your email address]";
$password = "[your email password]";
$host_conn = "{mail.domain.com:110/pop3/notls}INBOX";

# Non-secure IMAP - Change "mail.domain.com" to your IMAP server name
$username = "[your email address]";
$password = "[your email password]";
$host_conn = "{mail.domain.com:143/imap/notls}INBOX";

# Secure POP3 - NYU acct
$username = "[your NYU email address]";
$password = "[your NYU email password]";
$host_conn = "{mail.nyu.edu:995/pop3/ssl/novalidate-cert}INBOX";

# Secure IMAP - NYU acct
$username = "[your NYU email address]";
$password = "[your NYU email password]";
$host_conn = "{mail.nyu.edu:993/imap/ssl}INBOX";

# Secure IMAP - Gmail acct
$username = "[your Gmail email address]";
$password = "[your Gmail email password]";
$host_conn = "{imap.gmail.com:993/imap/ssl}INBOX";

*/

# Open a connection to the email server with the proper credentials
$mbox = imap_open($host_conn, $username, $password);

# Get the number of msgs
$num_msg = imap_num_msg($mbox);
print "Num of msgs: $num_msg\n";

# Loop through the msgs (email msgs start at 1)
for($msg_num=1; $msg_num<=$num_msg; $msg_num++)
{
  # Get the header info for the current msg and put into object
  $header_obj = imap_headerinfo($mbox,$msg_num);
	
  print "$msg_num: Message ID: " . $header_obj->message_id ."\n";
  print "$msg_num: Date: " . $header_obj->date ."\n";
  print "$msg_num: From: " . $header_obj->fromaddress ."\n";
  print "$msg_num: Subject: " . $header_obj->Subject ."\n";
}

# Close the connection
imap_close($mbox);

Creating PDFs in PHP   [top]
FPDF is a free PHP class which allows to generate PDF files with pure PHP and requires no special installation other than uploading a folder to your server account. There are other libraries available as well, but creating a "Hello, World" PDF using PHP and FPDF is as easy as:

<?
require "fpdf.php";

$pdf=new FPDF();
$pdf->AddPage();
$pdf->SetFont('Arial','B',16);
$pdf->Cell(40,10,'Hello World!');
$pdf->Output('output.pdf');
?>

Site Architecture Basics   [top]
One of the basic premises of building larger websites consisting of many pages is that you want to write a particular piece of code once and only once. If certain sections of PHP/HTML are used over and over throughout the site, then it is better to separate that code into its own PHP file, and then use the include or require keyword on that file whenever it is time for that code to appear.

If you look at the class notes carefully, you'll see that until the actual notes start, the top portion of the page is always the same. Similarly, you'll see that the bottom section below the horizontal line is always the same as well. These two chunks of code could be separated into their own files, say, header.php and footer.php. Then in our main PHP file, we could say:

<?
include "header.php";

# Write our main content here

include "footer.php";
?>

<b>ITP News Flashes</b>
<p>
<ul>
<li><a href="item.php?i=57">Boredom Overtakes DWD Class</a></li>
<li><a href="item.php?i=42">Dan O'Sullivan is America's Next Top Model</a></li>
<li><a href="item.php?i=79">New Swimming Pool Installed in P-Comp Lab</a></li>
</ul>

<?
$SqlStatement = "SELECT * FROM item WHERE id=".$_GET["i"];
?>

Thus, for interaction like this, we would need a template for the laundry list, and a template for the profile page. Let's see how these templates function in a sample site: Music 101

The Music 101 Demo Site

Music 101 Database Tables

Music 101 End-User Pages

Music 101 Admin Pages (un: itpdb - pw: interact)

HTML Template Integrated Templates (PEAR Module)

Related Resources   [top]