PHP source used in my URL shortener (uses the CodeIgniter framework)

controllers\url.php

<?php
/* Author: Peter Nelson / @_peterdn - controllers\url.php
 * The main controller for the site. */
 
	class Url extends Controller
	{
		public function Url()
		{
			parent::Controller();
			$this->load->helper("url");
		}
		
		public function index()
		{
			$this->load->view("url_create");
		}
				
		public function redirect()
		{
			$subs = explode("/", uri_string());
			$slug = $subs[3];
			
			$this->load->model("Urls_table");
			$url = $this->Urls_table->getUrlForSlug($slug);
			$this->Urls_table->incrementHits($slug);
			
			if ($url)
			{
				// Redirect to url or to a warning page,
				// depending on the urls perceived reputation.
				// Give the site the benefit of the doubt if we
				// can get no information about it.
				$rep = $this->_getUrlReputation($url);
				if ($rep && is_array($rep))
				{
					$min = 100;
					foreach ($rep as $name => $r)
						$min = $min < $r["reputation"] ? $min : $r["reputation"];
						
					if ($min < 60)
						redirect("/url/warning/$slug");
				}
				
				header("location: $url");
				exit();
			}
			else
			{
				redirect("/");
			}
		}
		
		public function warning()
		{			
			$subs = explode("/", uri_string());
			$slug = $subs[3];
			
			$this->load->model("Urls_table");
			$url = $this->Urls_table->getUrlForSlug($slug);
			
			if ($url)
			{
				$rep = $this->_getUrlReputation($url);
				$hostname = parse_url($url, PHP_URL_HOST);
				
				$data = Array("slug" => $slug, "url" => $url, 
				  "rep" => $rep, "hostname" => $hostname);
				$this->load->view("url_warning", $data);
			}
			else
			{
				redirect("/");
			}
		}
		
		public function create()
		{
			$url = $this->input->post("url");
			$url = filter_var($url, FILTER_VALIDATE_URL, FILTER_FLAG_SCHEME_REQUIRED);
			
			if (!$url)
				redirect("/");
			
			$this->load->model("Urls_table");
			
			$n = 5;
			$i = 0;
			do
			{
				$slug = $this->Urls_table->generateSlug($n);
				if ($n < 10 && ++$i % 5 == 0)
					++$n;
			}
			while ($this->Urls_table->doesSlugExist($slug));

			$date = new DateTime();
			$date = $date->format("Y-m-d H:i:s");
			
			$slug = $this->Urls_table->createUrlRow($url, $slug, $date, 0, 0);
						
			redirect("/url/view/$slug");
		}
		
		public function view()
		{
			$slug = $this->uri->segment(3);
			$this->load->model("Urls_table");
			if ($url = $this->Urls_table->getUrlForSlug($slug))
			{
				$rep = $this->_getUrlReputation($url);
				$hostname = parse_url($url, PHP_URL_HOST);
				$hits = $this->Urls_table->getHitsForSlug($slug);
				
				$data = Array("slug" => $slug, "url" => $url, 
				  "rep" => $rep, "hostname" => $hostname, "hits" => $hits);
				$this->load->view("url_view", $data);
			}
			else
			{
				redirect("/");
			}
		}
		
		public function privacy()
		{
			$this->load->view("url_privacy");
		}
		
		private function _getUrlReputation($url)
		{
			// URL reputation data provided by WOT
			// More info at http://www.mywot.com/wiki/API
			$attributes = array(0 => "Trustworthiness", 1 => "Vendor reliability",
			  2 => "Privacy", 4 => "Child safety");
			
			$r = new HttpRequest("http://api.mywot.com/0.4/public_query2",
			  HttpRequest::METH_GET);
			$r->setOptions(array("timeout" => 3));
			$r->addQueryData(array("url" => $url));
			try
			{
				$r->send();
				if ($r->getResponseCode() == 200)
				{
					// parse the XML response
					$doc = new DOMDocument();
					$doc->loadXML($r->getResponseBody());
					$qs = $doc->getElementsByTagName("query");
					if (!$qs || $qs->length < 1)
						return false;
					
					$q = $qs->item(0);
					$apps = $q->getElementsByTagName("application");
					if (!$apps)
						return false;
					
					$reps = array();
					$min = 100;
					for ($i = 0; $i < $apps->length; ++$i)
					{
						$a = $apps->item($i);
						$name = (int)$a->attributes->getNamedItem("name")->nodeValue;
						$rep = (int)$a->attributes->getNamedItem("r")->nodeValue;
						$min = $min < $rep ? $min : $rep;
						$conf = (int)$a->attributes->getNamedItem("c")->nodeValue;
						$reps[$attributes[$name]] = array("reputation" => $rep, "confidence" => $conf);
					}
					return $reps;
				}
			}
			catch (HttpException $ex)
			{
				return false;
			}
		}
	}

models\urls_table.php

<?php
/* Author: Peter Nelson / @_peterdn - models\urls_table.php
 * Manages getting / setting url data to / from the database */
 
	class Urls_table extends Model
	{
		public function Urls_table()
		{
			parent::Model();
			$this->load->database();		
		}
		
		public function generateSlug($n)
		{	
			$slug = "";
			for ($i = 0; $i < $n; ++$i)
			{
				$r = rand(0, 35);
				$slug .= $r < 10 ? chr(48+$r) : chr(97+($r-10));
			}
			return $slug;
		}
		
		public function getUrlForSlug($slug)
		{
			$query = $this->db->query("SELECT url FROM urls WHERE slug=?", 
			  array($slug));
			
			if ($query->num_rows() != 1)
				return false;
			
			if ($row = $query->row())			
				return $row->url;
			else
				return false;
		}	
		
		public function createUrlRow($url, $slug, $date, $hits, $flags)
		{
			$existing = $this->getSlugForUrl($url);
			if (!$existing)
			{
				$this->db->query("INSERT INTO urls VALUES(?, ?, ?, ?, ?)",
	   		  	  array($url, $slug, $date, $hits, $flags));
				return $slug;
			}
			return $existing;
		}
		
		public function doesSlugExist($slug)
		{
			$query = $this->db->query("SELECT id FROM urls WHERE slug=?",
			  array($slug));
			return $query->num_rows() == 1;
		}		
		
		public function getHitsForSlug($slug)
		{
			$query = $this->db->query("SELECT hits FROM urls WHERE slug=?",
			  array($slug));
			
			if ($query->num_rows() != 1)
				return false;
				
			$row = $query->row();
			return $row->hits;
		}
		
		public function incrementHits($slug)
		{
			$hits = $this->getHitsForSlug($slug);
			if ($hits === false)
				return false;
			
			++$hits;
			$this->db->query("UPDATE urls SET hits=? WHERE slug=?",
			  array($hits, $slug));
			return $this->db->affected_rows() == 1;
		}
		
		public function getSlugForUrl($url)
		{
			$q = "SELECT slug FROM urls WHERE url=?";
			$query = $this->db->query($q, array($url));
			
			if ($query->num_rows() < 1)
				return false;
			
			if ($row = $query->row())			
				return $row->slug;
			else
				return false;
		}
	}

views\url_create.php

<!DOCTYPE html>
<html lang="en">
<head>
  <title>pdn.to | URL shortener</title>
  <meta charset="utf-8" />
  <link rel="shortcut icon" href="<?php echo THEMEPATH."/favicon.png"; ?>" type="image/png"/>
  <style>
    @import url('<?php echo THEMEPATH."/global.css"; ?>');
  </style>
  <script src="<?php echo SCRIPTPATH."/glow/1.7.3/core/core.js"; ?>"></script>
  <script src="<?php echo SCRIPTPATH."/qrcode.js"; ?>"></script>
  <script src="<?php echo SCRIPTPATH."/buttons.js"; ?>"></script>
  <!--[if IE]><script src="http://html5shiv.googlecode.com/svn/trunk/html5.js"></script><![endif]-->
</head>
<body>
<section id="main">
<header>
<div style="text-align:center"><a href="http://pdn.to"><img src="<?php echo THEMEPATH."/logo.png"; ?>" alt="pdn.to | URL shortener" width="365" height="35" /></a></div>
</header>
<section id="createurl">
<form method="post" action="/index.php/url/create">
<p><input type="text" name="url" id="the_url" class="url" autocomplete="off" /></p>
<p><button type="submit" id="shorten" value="shorten">Shorten</button>
<button type="button" id="qrcode" value="qrcode">QR Code</button></p>
</form>
</section>
<section id="qrcode_info">
<h2 id="qrcode_title"></h2>
<p id="qrcode_error" class="error">
</p>
<p id="qrcode_container">
<canvas id="qrcode_canvas"></canvas>
</p>
</section>
</section>
<footer>
<p><small>All content copyright &copy; <a href="http://peterdn.com">Peter Nelson</a> 2010 | <a href="/index.php/url/privacy">Privacy Policy</a></small></p>
</footer>
</body>
</html>

views\url_view.php

<!DOCTYPE html>
<html lang="en">
<head>
  <title>pdn.to | URL shortener</title>
  <meta charset="utf-8" />
  <link rel="shortcut icon" href="<?php echo THEMEPATH."/favicon.png"; ?>" type="image/png"/>
  <style>
    @import url('<?php echo THEMEPATH."/global.css"; ?>');
  </style>
  <script src="<?php echo SCRIPTPATH."/Silverlight.js"; ?>"></script>
  <script src="<?php echo SCRIPTPATH."/glow/1.7.3/core/core.js"; ?>"></script>
  <script src="<?php echo SCRIPTPATH."/qrcode.js"; ?>"></script>
  <script src="<?php echo SCRIPTPATH."/buttons.js"; ?>"></script>
  <script src="<?php echo SCRIPTPATH."/linkbox.js"; ?>"></script>
  <!--[if IE]><script src="http://html5shiv.googlecode.com/svn/trunk/html5.js"></script><![endif]-->
</head>
<body>
<section id="main">
<header>
<div style="text-align:center"><a href="http://pdn.to"><img src="<?php echo THEMEPATH."/logo.png"; ?>" alt="pdn.to | URL shortener" width="365" height="35" /></a></div>
</header>
<section id="createurl">
<form method="post" action="/index.php/url/create">
<div id="info"><p>Your Link:</p></div>
<div id="linkbox"><input type="text" id="the_url" class="yourlink" value="http://pdn.to/<?php echo $slug; ?>" readonly="readonly" />
<div id="linkslbox"></div></div>
<div class="clear"></div>
<p><input type="text" name="url" class="url" autocomplete="off" value="<?php echo $url; ?>" /></p>
<p><button type="submit" name="op" id="shorten" value="shorten">Shorten</button>
<button type="button" name="op" id="qrcode" value="qrcode">QR Code</button></p>
</form>
</section>
<section id="qrcode_info">
<h2 id="qrcode_title"></h2>
<p id="qrcode_error" class="error">
</p>
<p id="qrcode_container">
<canvas id="qrcode_canvas"></canvas>
</p>
</section>
<section id="url_reputation">
<h2>Reputation of <?php echo $hostname; ?></h2>
<?php if ($rep) { ?>
<table>
<thead><tr><th>Description</th><th>Reputation<br />Estimate</th><th>Estimate<br />Reliability</th></tr></thead>
<?php 
$n = 0;
$avg = 0;
foreach ($rep as $name => $data) 
{
	++$n;
	echo "<tr><td>$name</td><td>";	
	$r = $data["reputation"];
	$avg += $r;
	$c = $data["confidence"];
	if ($r < 20) echo "<span class=\"verypoor\">Very poor</span>";
	else if ($r >= 20 && $r < 40) echo "<span class=\"poor\">Poor</span>";
	else if ($r >= 40 && $r < 60) echo "<span class=\"unsatisfactory\">Unsatisfactory</span>";
	else if ($r >= 60 && $r < 80) echo "<span class=\"good\">Good</span>";
	else if ($r >= 80) echo "<span class=\"excellent\">Excellent</span>";
	echo "</td><td>";	
	if ($c < 23) echo "<span class=\"unsatisfactory\">Uncertain</span>";
	else if ($c >= 23) echo "<span class=\"excellent\">Certain</span>";
	echo "</td></tr>";
}
$avg /= $n;
echo "</table><p>Overall: <strong>";
if ($avg < 20) echo "<span class=\"verypoor\">Very poor</span>";
else if ($avg >= 20 && $avg < 40) echo "<span class=\"poor\">Poor</span>";
else if ($avg >= 40 && $avg < 60) echo "<span class=\"unsatisfactory\">Unsatisfactory</span>";
else if ($avg >= 60 && $avg < 80) echo "<span class=\"good\">Good</span>";
else if ($avg >= 80) echo "<span class=\"excellent\">Excellent</span>";
echo "</strong></p>";
?>
<p>The table above provides information about this URL using data gathered by the <a href="http://www.mywot.com">Web of Trust (WOT)</a>. 
It shows an estimate of how highly the website scores on each of four attributes, and a measure of how accurate each estimate is deemed to be.</p>
<?php } else { ?>
<p class="error">No reputation information available for this URL</p>
<?php } ?>
</section>
<section id="statistics">
<h2>Statistics</h2>
<p>Total hits: <strong><?php echo $hits; ?></strong></p>
</section>
</section>
<footer>
<p><small>All content copyright &copy; <a href="http://peterdn.com">Peter Nelson</a> 2010 | <a href="/index.php/url/privacy">Privacy Policy</a></small></p>
</footer>
</body>
</html>

views\url_warning.php

<!DOCTYPE html>
<html lang="en">
<head>
  <title>pdn.to | URL shortener</title>
  <meta charset="utf-8" />
  <link rel="shortcut icon" href="<?php echo THEMEPATH."/favicon.png"; ?>" type="image/png"/>
  <style>
    @import url('<?php echo THEMEPATH."/global.css"; ?>');
  </style>
  <!--[if IE]><script src="http://html5shiv.googlecode.com/svn/trunk/html5.js"></script><![endif]-->
</head>
<body>
<section id="main">
<header>
<div style="text-align:center"><a href="http://pdn.to"><img src="<?php echo THEMEPATH."/logo.png"; ?>" alt="pdn.to | URL shortener" width="365" height="35" /></a></div>
</header>
<section id="url_reputation">
<p class="warning">Warning: The website at <?php echo $hostname; ?> was deemed to be unsafe due to the reasons given below. 
If you are certain that you wish to proceed, please <a href="<?php echo $url; ?>" rel="nofollow">follow this link</a>.</p>
<h2>Reputation of <?php echo $hostname; ?></h2>
<?php if ($rep) { ?>
<table>
<thead><tr><th>Description</th><th>Reputation<br />Estimate</th><th>Estimate<br />Reliability</th></tr></thead>
<?php 
$n = 0;
$avg = 0;
foreach ($rep as $name => $data) 
{
	++$n;
	echo "<tr><td>$name</td><td>";	
	$r = $data["reputation"];
	$avg += $r;
	$c = $data["confidence"];
	if ($r < 20) echo "<span class=\"verypoor\">Very poor</span>";
	else if ($r >= 20 && $r < 40) echo "<span class=\"poor\">Poor</span>";
	else if ($r >= 40 && $r < 60) echo "<span class=\"unsatisfactory\">Unsatisfactory</span>";
	else if ($r >= 60 && $r < 80) echo "<span class=\"good\">Good</span>";
	else if ($r >= 80) echo "<span class=\"excellent\">Excellent</span>";
	echo "</td><td>";	
	if ($c < 23) echo "<span class=\"unsatisfactory\">Uncertain</span>";
	else if ($c >= 23) echo "<span class=\"excellent\">Certain</span>";
	echo "</td></tr>";
}
$avg /= $n;
echo "</table><p>Overall: <strong>";
if ($avg < 20) echo "<span class=\"verypoor\">Very poor</span>";
else if ($avg >= 20 && $avg < 40) echo "<span class=\"poor\">Poor</span>";
else if ($avg >= 40 && $avg < 60) echo "<span class=\"unsatisfactory\">Unsatisfactory</span>";
else if ($avg >= 60 && $avg < 80) echo "<span class=\"good\">Good</span>";
else if ($avg >= 80) echo "<span class=\"excellent\">Excellent</span>";
echo "</strong></p>";
?>
<p>The table above provides information about this URL using data gathered by the <a href="http://www.mywot.com">Web of Trust (WOT)</a>. 
It shows an estimate of how highly the website scores on each of four attributes, and a measure of how accurate each estimate is deemed to be.</p>
<?php } else { ?>
<p class="error">No reputation information available for this URL</p>
<?php } ?>
</section>
</section>
<footer>
<p><small>All content copyright &copy; <a href="http://peterdn.com">Peter Nelson</a> 2010 | <a href="/index.php/url/privacy">Privacy Policy</a></small></p>
</footer>
</body>
</html>

Post about this here - http://peterdn.com/page/upeterdncom-URL-shortener.aspx