PHP

Sometimes you will want to get a random value form an array in a biased random way, that is, you will want certain values to be returned more than others. Here is a function that will generate a single key from an array, with a greater change of a higher value being retrieved.

function biasedRandom($numbers){
 $total = 0;
 foreach($numbers as $number=>$weight){
  $total += $weight;
  $distribution[$number] = $total;
 };
 $rand = mt_rand(0,$total-1);
 foreach($distribution as $number=>$weights){
  if($rand<$weights){
   return $number;
  };
 };
}

This function is used in the following way.

Inserting a value into a database with an auto incrementing field is quite common. Once you insert the new row you would expect that you need to do another query to get the newly created ID.

Another option is to use the mysql_insert_id() function to retrieve the ID created by the last insert statement.

// insert
$sql = 'INSERT INTO table(colum1, colum2) VALUES(1, 2);';
mysql_query($sql);
 
// get new id
$id = mysql_insert_id();

The $id variable will now contain your most recently inserted ID.

Here is a very simple function that will generate a string of random characters, ideal if you want to create a password for a new user.

function generatePassword($length=10)
{
 $pass = '';
 $parts = array_merge(range(0, 9),range('a', 'z'),range('A', 'Z'));	
 for ($i=0; strlen($pass) <= $length; $i++) {
  $pass .= $parts[array_rand($parts)];
 }
 return $pass;
}

Use the function like this.

echo generatePassword();

To create a longer password string just pass a parameter with the function.

echo generatePassword(5);

Use the following function to extract all of the links from a HTML string.

function linkExtractor($html)
{
 $linkArray = array();
 if(preg_match_all('/<a\s+.*?href=[\"\']?([^\"\' >]*)[\"\']?[^>]*>(.*?)<\/a>/i', $html, $matches, PREG_SET_ORDER)){
  foreach ($matches as $match) {
   array_push($linkArray, array($match[1], $match[2]));
  }
 }
 return $linkArray;
}

To use it just read a web page or file into a string, and pass that string to the function. The following example reads a web page using the PHP CURL functions and then passes the result into the function to retrieve the links.

Spam is a problem. You want to allow people who genuinely want to get in touch to see your email address, but doing this invariably leads to you getting thousands of spam emails.

One solution is to hide your email address in an image, but it can be a pain to create an image for every email address you need. A better solution is to use the PHP GD functions to create an image at runtime so that your email address is displayed, but is completely unreadable to spammers.

To to this you will need to create an image tag on your website, here is an example.

Here are two ways in which you can figure out all of the different permutations of an array.

The first is using a recursive algorithm. This nibbles apart the array and sticks it back together again, eventually resulting in all of the different permutations available.

Wordpress widgets are a way to customise the sidebar of your blog very easily and where included with the default Wordpress instillation from version 2.2 onwards. With a widgetised theme all you need to do to change the menu system on your blog is drag and drop features and edit some simple parameters like heading.

To include widgets on your blog you need a widget ready Wordpress theme. However, this isn't as easy as it sounds because only a small section of themes are widget enabled.

To make a widget enabled theme you can use any existing theme and just a few lines of code. First off, find the file called sidebar.php in your Wordpress theme directory. You might not have this file, but you are looking for the section of code that displays the navigation menu.

You can display your latest Wordpress posts anywhere on your site by using an RSS reader called SimplePie and a few lines of code. SimplePie is a fast and efficient RSS reader, and it will also cache feeds to reduce the amount of processing time taken.

Download simple pie from the website and upload the simplepie.inc file to your web server. Next include the following section of code anywhere on your site that you want to display the latest post on.

When you supply files that web browsers can open they are usually opened inside the browser, rather than being downloaded. This can be annoying, especially where PDF documents are involved. You could supply the files in a compressed format in order to force users to download them, but this is also annoying as the user then has to uncompress the file.

You can force the web browser to supply the file as a download by using the header() function in PHP. The following little bit of code will take any filename and supply it as a download.

<?php
$file = $_GET['file'];
header('Content-type: octet/stream');
header('Content-disposition: attachment; filename='.$file.';');
header('Content-Length: '.filesize($file));
readfile($file);
exit;
?>

All you have to do is link to this script with the argument being the file name you want your users to be able to download.

For most functions it is normal for have the function return the output of a calculation. With PHP it is also possible to pass values to the function by reference. A better way of saying this is rather than pass the value of the variable you pass a pointer to the variable itself. When you do this anything that you do to the variable inside the function is also done outside, so if you interact with the variable again it will contain a different value.

The ampersand (&) character is used in the parameters of the function to stipulate that a parameter will be passed by reference.

Here is an example of this at work.