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Swapping variable values is important in sorting algorithms when you want to swap a higher value with a lower one. The usual action of variable assignment is to take the first value, put the value of this variable in a temporary variable and then assign the value of the second variable to the first one. As in the following code:

$tmp = $a;
$a = $b;
$b = $tmp;

This can be rewritten using the bitwise Xor (exclusive or) operator.

$a = $a ^ $b;
$b = $b ^ $a;
$a = $a ^ $b;

This can also be written in the shorthand notation as follows:

$a ^= $b;
$b ^= $a;
$a ^= $b;

I have already talked about converting a sitemap.xml file into a urllist.txt file, but what if you want to create a HTML sitemap? If you have a sitemap.xml file then you can use this to spider your site, scrape the contents of each page and populate the HTML file with this information.

The following code does this. For every page it looks for the title tag, the description meta tag and the first h2 tag on the page. These items are then used to construct a segment of HTML for that page.

If you create a script that produces a sitemap.xml file there is no point in adapting this script so that it creates a urllist.txt file. The best solution is to use this sitemap.xml file to create the urllist.txt. The following script will do exactly this.

An ordinal number is just a way of saying that position the number is in. So for the number 1 the ordinal version of this is 1st. 2 is 2nd, 3 is 3rd and so on.

The following function will work out what ordinal text should be placed behind a number. This will be one of 'st', 'nd', 'rd' and 'th'.

function getOrdinal($number){
 // get first digit
 $digit = abs($number) % 10;
 $ext = 'th';
 // if the last two digits are between 4 and 21 add a th
 if(abs($number) %100 < 21 && abs($number) %100 > 4){
  $ext = 'th';
 }else{
  if($digit < 4){
   $ext = 'rd';
  }
  if($digit < 3){
   $ext = 'nd';
  }
  if($digit < 2){
   $ext = 'st';
  }
  if($digit < 1){
   $ext = 'th';
  }
 }
 return $number.$ext;
}

This set of if statements can be shortened by using the ternary control structure.

phpMyAdmin is a tool, written in PHP, that allows you to handle the administration of a MySQL database server. You could always download the MySQL GUI tools, but the problem there is that you need to give external access to a user account, which isn't always possible to do. This is where phpMyAdmin steps in.

The tool is easy to use and I have done some tricky stuff with it in the past. It can do everything that you need it to do with MySQL.

Use the following function to remove all duplicate values in an array.

function remove_duplicated_values($array){
 $newArray = array();
 foreach($array as $key=>$val){
  $newArray[$val] = 1;
 }
 return array_keys($newArray);
}

The way this function works is by looping through the array and assigning each value of the array to be a key of a new array and setting the value as 1. As the values of the array are added to the new array any new values will lengthen the array and any duplicate values will reset to be 1.

The keys of the new array are then returned as an array of values using the array_keys() PHP function.

Here is an example of the function in action.

Printing out stuff with PHP is basically essential to any program, but problems can arise if you want to use the same script for command line scripting and web site scripting because of the need to print out HTML. The $_SERVER super global array contains a variable called SERVER_PROTOCOL, which contains the protocol that the client is using to access the script. If the client access through the web then the protocol will contain something like "HTTP 1.1". If the script is being run from the command line then this super global variable SERVER_PROTOCOL would exist.

It would therefore be possible to print out HTML or new line characters depending on if the protocol variable exists. The following function can be used instead of the print() function to print out an HTML <br /> tag when the SERVER_PROTOCOL variable exists and new lines when it is not present.

Lots of applications require a user to input a URL and lots of problems occur as a result. I was recently looking for something that would take a URL as an input and allow me to make sure that is was formatted properly. There wasn't anything that did this so I decided to write it myself.

The following function takes in a URL as a string and tries to clean it up. It essentially does this by splitting is apart and then putting it back together again using the parse_url() function. In order to make sure that this function works you need to put a schema in front of the URL, so the first thing the function does (after trimming the string) is to check that a schema exists. If it doesn't then the function adds this onto the end.

Getting users to enter a list of items is a normal practice, but getting users to do it properly is sometimes a challenge in itself. Some users will put spaces in between the commas, others will not, some will even put a trailing comma at the end of the list.

Here is some code that can be used to clear up a comma separated list using some simple regular expressions. It works using the preg_replace() function, and by passing this function an array of options patterns and an array of replacements.

$list= trim($list);
$patterns[0] = '/\s*,\s*/';
$patterns[1] = '/,{2,}/';
$patterns[2] = '/,+$/';
$patterns[3] = '/^,+/';
$replacements[0] = ',';
$replacements[1] = ',';
$replacements[2] = '';
$replacements[3] = '';
$list= preg_replace($patterns, $replacements, $list);

Take the following string, entered by a user at 2 o'clock in the morning, whilst surfing the net drunk after coming home from the pub.

I found a good function that details how to format numbers with commas in JavaScript and thought I would reproduce it here. It basically takes any number and turns it into formatted string with the thousands separated by commas. The number_format() function is available in PHP and I have been relying on PHP to sort out the formatting before returning it via an AJAX call. I can now include this function into my JavaScript library and do this on the client side.

The function works by using regular expressions to first split the string into whole number and decimal, before splitting the number by groups of three digits.

The regular expression used is (\d+)(\d{3}), which looks for a sequence of three numbers preceded by any numbers. This is a little trick that causes the regular expression engine to work from right to left, instead of left to right.