PHP

To redirect to a different page using PHP you can use the header() function with the parameter 'Location: ' and the destination of the redirect.

header('Location: http://www.hashbangcode.com');

However, if any headers are sent before this function call then the script will fail. To get around this you can either ensure that nothing is printed out on the page, or if that is not possible for some reason then you can use a JavaScript redirect. The headers_sent() function will allow you to see if any headers have been sent to the browser yet, if they have then you will need to use the JavaScript redirect like this:

Working out the average of a bunch of values is quite a common task, but rather than looping through the array, adding together values as you go and the using the count() function to find out the average at the end.

function average($array)
{
 $total = 0;
 foreach ($array as $item) {
  $total += $item;
 };
 return $total/count($array);	
}

However, a much simpler way of doing things is just to use the PHP function array_sum(), which adds up all of the values in the array. Because this is done by the PHP engine it should take less time than using a for loop.

function average($array) {
 return array_sum($array) / count($array);
}

Tests show that the second function is only just faster when using short (2 or 3 items) arrays, but the second function is significantly faster when looking at longer (10 or more) arrays.

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.

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.