Archive for June 2009
Format a time interval with the requested granularity
This class, a refactored version of Drupal’s format_interval function, makes it relatively easy to format an interval value. The format will automatically format as compactly as possible. For example: if the difference between the two dates is only a few hours and both dates occur on the same day, the year, month, and day parts of the date will be omitted.
class DateIntervalFormat
{
/**
* Format an interval value with the requested granularity.
*
* @param integer $timestamp The length of the interval in seconds.
* @param integer $granularity How many different units to display in the string.
* @return string A string representation of the interval.
*/
public function getInterval($timestamp, $granularity = 2)
{
$seconds = time() - $timestamp;
$units = array(
'1 year|:count years' => 31536000,
'1 week|:count weeks' => 604800,
'1 day|:count days' => 86400,
'1 hour|:count hours' => 3600,
'1 min|:count min' => 60,
'1 sec|:count sec' => 1);
$output = '';
foreach ($units as $key => $value) {
$key = explode('|', $key);
if ($seconds >= $value) {
$count = floor($seconds / $value);
$output .= ($output ? ' ' : '');
if ($count == 1) {
$output .= $key[0];
} else {
$output .= str_replace(':count', $count, $key[1]);
}
$seconds %= $value;
$granularity--;
}
if ($granularity == 0) {
break;
}
}
return $output ? $output : '0 sec';
}
}
Usage:
$dateFormat = new DateIntervalFormat();
$timestamp = strtotime('2009-06-21 20:46:11');
print sprintf('Submitted %s ago', $dateFormat->getInterval($timestamp));
Outputs:
Submitted 3 days 4 hours ago
Face Detection Using PHP
Maurice Svay explains how to detect faces in photos with PHP:
Nowadays, face detection is built in many consumer products (camera obviously, but also Google and iPhoto), and seems to be a pretty common job. So I expected to find many solutions for doing it with PHP. Surprisingly, the only one I could find is OpenCV, an opensource lib that was originally developed by Intel. OpenCV seems to perform well but you need to be able to install it on your server. In my case, I wanted to have a pure PHP solution, so it can work with most hosts.
Apache HTTP DoS tool released
Yesterday an interesting HTTP DoS tool has been released. The tool performs a Denial of Service attack on Apache (and some other, see below) servers by exhausting available connections. While there are a lot of DoS tools available today, this one is particularly interesting because it holds the connection open while sending incomplete HTTP requests to the server.
Java, C, Python and nested loops
Java has no goto statement, to break or continue multiple-nested loop or switch constructs, Java programmers place labels on loop and switch constructs, and then break out of or continue to the block named by the label. The following example shows how to use java break statement to terminate the labeled loop:
public class BreakLabel
{
public static void main(String[] args)
{
int[][] array = new int[][]{{1,2,3,4},{10,20,30,40}};
boolean found = false;
System.out.println("Searching 30 in two dimensional int array");
Outer:
for (int intOuter = 0; intOuter < array.length ; intOuter++) {
Inner:
for (int intInner = 0; intInner < array[intOuter].length; intInner++) {
if (array[intOuter][intInner] == 30) {
found = true;
break Outer;
}
}
}
if (found == true) {
System.out.println("30 found in the array");
} else {
System.out.println("30 not found in the array");
}
}
}
Use of labeled blocks in Java leads to considerable simplification in programming effort and a major reduction in maintenance.
On the other hand, the C continue statement can only continue the immediately enclosing block; to continue or exit outer blocks, programmers have traditionally either used auxiliary Boolean variables whose only purpose is to determine if the outer block is to be continued or exited; alternatively, programmers have misused the goto statement to exit out of nested blocks.
What’s interesting is that Python rejected the labeled break and continue proposal a while ago. And here’s why:
Guido van Rossum wrote:
I’m rejecting it on the basis that code so complicated to require this feature is very rare. While I’m sure there are some (rare) real cases where clarity of the code would suffer from a refactoring that makes it possible to use return, this is offset by two issues:
1. The complexity added to the language, permanently.
2. My expectation that the feature will be abused more than it will be used right, leading to a net decrease in code clarity (measured across all Python code written henceforth). Lazy programmers are everywhere, and before you know it you have an incredible mess on your hands of unintelligible code.
But what’s more interesting is that the idea of adding a goto statement was never mentioned. Common sense perhaps?
Google Page Speed: Web Performance Best Practices
When you profile a web page with Page Speed, it evaluates the page’s conformance to a number of different rules. These rules are general front-end best practices you can apply at any stage of web development. Google provides documentation of each of the rules, so whether or not you run the Page Speed tool, you can refer to these pages at any time.
The best practices are grouped into five categories that cover different aspects of page load optimization:
- Optimizing caching: Keeping your application’s data and logic off the network altogether
- Minimizing round-trip times: Reducing the number of serial request-response cycles
- Minimizing request size: Reducing upload size
- Minimizing payload size: Reducing the size of responses, downloads, and cached pages
- Optimizing browser rendering: Improving the browser’s layout of a page
The Cost of Hosting on Amazon
Mather Corgan, president of HotPads, gave a great talk on how HotPads uses AWS to run their real estate search engine. HotPads abandoned their managed hosting in December and took the leap over to EC2 and its siblings. The presentation has a lot of detail on costs and other things to watch out for, so if you’re currently planning your “cloud” architecture, you’ll find some of this really helpful.
