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Deziner Folio posted this PHP snippet for creating a simple back link that will take you to the previous page you were on.

Code:

PHP:

<?php session_start(); ?> <!– Starting a session before the DOCTYPE –>
<!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Strict//EN”
“http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd”>
<a href=”<?php echo $_SESSION[’back’]; ?>“>back</a> <!–The anchor tag that links to the previous page –>
<?php $_SESSION[’back’] = $_SERVER[’REQUEST_URI’]; ?> <!– Assigning the current URL to a session variable –>

Please note that first we assign the previous session variable to the anchor tag and only then re-assign the current URL to the session variable which will be read when you move on to the next page.

This being a simple PHP snippet can be used in almost every CMS (PHP based) and sure is a good addon to the accessibility of your site.

You can view the original article here

Posted in Programming

Recover Truncated PHP Serialized Arrays

January 8th, 2008

Shaun Inman has posted a great function that will salvage all the data that it can in a serialized array that has been truncated. PHP's unserialize() function will fail if it encounters a malformed string. This is where repairSerializedArray() function comes in to save the day.

PHP’s native serialization text format is the simplest way to store an arbitrary array in a database without losing the types of its many values or their structure within the array. However, you might occasionally run into problems when the serialized string is longer than the database column that houses it. The resulting truncated string cannot be unserialized by PHP. The majority of the data might still be intact but PHP doesn’t know what to do with it; so I wrote a function, two actually, that does. (While PHP’s serialize() and unserialize() functions also work with objects this recovery function does not.)

Because the recursive function operates on and whittles down the actual serialized string while it attempts its recovery, a second function duplicates and prepares the string leaving the original unchanged.

Code Example

PHP:

// the native unserialize() function returns false on failure
$data = @unserialize($serialized); // @ silences the default PHP failure notice
if ($data === false) // could not unserialize
{
$data = repairSerializedArray($serialized); // salvage what we can
}

You can read the full post and download the code here

Posted in Programming

Random Images with PHP

December 6th, 2007

Devlounge has posted an article for displaying random images with PHP.

Every now and then you want to randomize images, usually headers of sorts. This is pretty simple, with just 9 lines of PHP code you can rotate randomly between two images.

PHP:

<?php
$images = array(
0 => 'image1.gif',
1 => 'image2.gif',
);
$image = $images[ rand(0,(count($images)-1)) ];
$output = "<img src=\"/mysite/randomimages/".$image."\" alt=\"\" border=\"0\" />";
print($output);
?>

This will rotate between image1.gif and image2.gif, which are located in /mysite/randomimages/ on your server.

Check out the full post here

Posted in Programming

Limit File Download Speed with PHP

November 1st, 2007

This PHP code will limit the download rate for a file being downloaded by a client. This is useful if you are streaming MP3s from your site and you are trying to distribute your bandwidth as evenly as possible.

For example: If you are streaming MP3s with a bitrate of 96kb then you would at the minimum only need to send 12KB/s of data to the client. Now to be safe I would send around 16KB/s to allow some buffering just in case some packets get held up somewhere.

Code

PHP:

<?php
$file = "/path/to/file/test.mp3"; // path to file
$speed = 16; // 16 kb/s download rate limit
header("Cache-control: private");
header("Content-Type: application/octet-stream");
header("Content-Length: ".filesize($file));
header("Content-Disposition: filename=$file" . "%20");
flush();
$fd = fopen($file, "r");
while(!feof($fd)) {
echo fread($fd, round($speed*1024));
flush();
sleep(1);
}
fclose ($fd);
?>

Posted in Programming

Random Password Generator with PHP

October 3rd, 2007

This function will generate a random password based off of a character list that you specify. This is very useful for a user registration form.

Example: Instead of asking a user for their desired password on a sign up form, generate a random one for them and email it to them. This poses less of a security risk by emailing them a random password and less fields for them to to fill out when signing up.

PHP:

function randomPassword($length = 7) {
// empty password
$password = "";
// define possible characters
$possible = "23456789abcdefghjkmnpqrstuvwxyz";
// add random characters until $length is reached
$i = 0;
while ($i <$length) {
// pick a random character from the possible ones
$char = substr($possible, mt_rand(0, strlen($possible)-1), 1);
// don't allow duplicate characters
if (strpos($password, $char) === false) {
$password .= $char;
$i++;
}
}
return $password;
}

Posted in Programming

List all files in a directory with PHP

October 2nd, 2007

This code snippet displays a hyper linked list of all the files contained in a specified folder. I find myself always coming back to this very useful piece of code. I can't count how many times I've used this.

PHP:

<?
// Define the full path to the folder whose contents you want to list
$path = "/home/user/public/foldername/";
// Open the directory
$dir_handle = @opendir($path) or die("Error opening $path");
// Loop through the files
while ($file = readdir($dir_handle)) {
if($file == "." || $file == ".." || $file == "index.php" ) { continue; }
echo "<a href=\"$file\">$file</a><br />";
}
// Close
closedir($dir_handle);
?>

Posted in Programming

MySQL Update on Duplicate entries for Inserts

September 27th, 2007

Particletree has a great article on a MySQL query that updates a record in a database when trying to insert data that has a record with a duplicate key. Check out the code below.

Old Way

PHP:

$sql = 'SELECT TransId FROM Sales WHERE TransId = 123';
$rs = $db->query($sql);
if(mysql_num_rows($rs) == 1) {
// do an SQL UPDATE
}
else {
// do an SQL INSERT
}

New Way

SQL:

INSERT INTO Sales(TransId, STATUS, Amount)
VALUES(123, 'Pending', 20)
ON DUPLICATE KEY UPDATE STATUS = 'Paid'

~~Also keep in mind that a current bug in MySQL makes this method not replication safe.~~ I believe this has been fixed.

Posted in Programming

7 reasons I switched back to PHP after 2 years on Rails

September 24th, 2007

Derek Sivers, the founder, president, and sole programmer behind CD Baby, wrote a great article about why he switched back to PHP from Rails. I have nothing against Ruby or Rails, but I never found the reason why everyone was so hyped about it. Check out the article below.

“Is there anything Rails can do, that PHP CAN’T do?”

The answer is no.

I threw away 2 years of Rails code, and opened a new empty Subversion respository.

Article:
7 reasons I switched back to PHP after 2 years on Rails

Posted in Rants

Convert Multiple Spaces To a Single Space

July 25th, 2007

Nifty line of PHP code that will take multiple sequential spaces and convert into a single space. This is great for cleaning and sanitizing data before storing it.