To randomise an array in PHP use the shuffle() function like this.

$array = range(1, 5);
shuffle($array); // randomise array

There are two limitations to this function. The first is that it completely removes any key association that you may have set up. So the following array.

$array = array('one'=>1,'two'=>2);

Would be turned into the following after using shuffle().

Array
(
  [0] => 2
  [1] => 1
)

A way around this is to use the following function, this uses the PHP function array_rand() to extract the all of the keys in the array in a random order before ensuring that the key associations are in place.

It is widely known that the data that Alexa offers on visitor numbers is far from accurate, but it is possible to obtain an XML feed from Alexa that allows you to find out all of the data that Alexa offers, which is more than just their visitor numbers. Passing the correct parameters to this feed you can find out related links, contact and domain information, the Alexa rank, associated keywords and Dmoz listings.

As an example here is a feed URL for getting information about the bbc.co.uk page.

http://xml.alexa.com/data?cli=10&dat=nsa&ver=quirk-searchstatus&uid=19700101000000&userip=127.0.0.1&url=www.bbc.co.uk

So to get information about any site all you have to do is pass the correct URL to this address.

To get this information in a usable form with PHP you can use the curl functions. To download the Alexa feed into PHP use the following code:

The str_word_count() function in PHP does exactly what is says it does. The default of this function is to simply count the number of words present. Take the following string.

$str = "This is a 'string' containing m0re than one word. This is a 'string' containing m0re than one word.";

If we pass this to the str_word_count() function with no other parameters we get the number of words.

echo str_word_count($str); // prints 20

The second parameter is the type of value returned from the function. The default value is 0, but 1 and 2 are also available. Using 1 as the second parameters returns an array containing all the words found inside the string. Using 2 returns an associative array, where the key is the numeric position of the word inside the string and the value is the actual word itself. Here are the results from setting the second parameter to 1.

Using a simple .htpasswd to password protect a directory or website is fine if you only have a few users, and they don't change very much. However, this quickly becomes impossible to maintain if you have lots of users. For example, if you wanted to secure access to the company Intranet you might spend quite some time trying to update your .htpasswd file. The best way to do this is to transfer all of the user administration over to an LDAP server and then get Apache to communicate with this directly. The Active Directory (AD) system that Microsoft uses allows LDAP communications, and as this is in use across many company networks it is an ideal candidate to use.

You first need to set of the LDAP modules on your Apache server. Uncomment or add the following lines in your http.conf file. You will need to make sure that the files actually exist as well.

If you have programmed in PHP for any amount of time then you will be farmiliar with the if statement. The syntax is as follows:

if($something == $somethingelse){
  //do something
}elseif($something == $anotherthing){
  //do another thing
}else{
  // default action
}

The PHP engine also allows you to do what I call "lazy programming" where you don't need the curly braces. Only the line underneath the if statement is run if the if clause if met.

if($something == $somethingelse)
  // do something

The issue here is that when this is put into the rest of the program the code becomes almost unreadable and therefore unmaintainable. The curly brases make it much easier to see what a program is doing. For readability and maintenance, many developers consider it bad style not to include them.

Sometimes in PHP you will have to do some things that might take a little time. You will therefore have a little trouble with users closing the browser or moving to another page before the script has finished. In this case you will want to either continue to execute the script just shut it down depending on what the user has done.

PHP will not detect that the user has aborted the connection until an attempt is made to send information to the client. Simply using an echo statement does not guarantee that information is sent. Use the flush() function after the echo call to force PHP to sent output information to the browser.

To run the script to the end no matter what the user has done use the ignore_user_abort() function with the parameter of true.

ignore_user_abort(true);

This might be useful if you are recording things to a database so that data integrity is still maintained.

PHP keeps certain variables to do with server and networking in an associative array called SERVER. To find out the remote address of a user you can use the array identifier REMOTE_ADDR. This is used in the following manner.

$ipaddress = $_SERVER['REMOTE_ADDR'];

This IP address can be passed into the gethostbyaddr() function to find out host name associated with the specified IP address.

After installing PHP on Apache you can use the php.ini file to set various different options to do with PHP. When Apache starts it uses what is contained in this file to set up and run PHP.

On both Windows, Unix and Linux systems Apache will look in a number of default locations for the php.ini file before giving up. You can explicitly tell Apache 2.x where to look for the file by using the PHPIniDir directive in the http.conf file.

#
# This is the directory containing php.ini
#
PHPIniDir "/usr/local/apache/conf"

For Apache 1.3.x this can be set using the SetEnv PHPRC directive.

# specify the directory where php.ini is
SetEnv PHPRC /usr/local/apache/conf

This not only speeds up the time taken for Apache to start, but will also allow you to make sure that the php.ini file you are using is the one you are editing.

All of the maths functions in JavaScript are kept in a handy object called Math, which contains a number of different functions.

To get the absolute value of a number use the abs() function.

Math.abs(3.14159265) // returns 3.14159265

Rounding a number is done by either the round() function to round to the nearest integer, the ceil() function to round up to the nearest integer and the floor() function to round down to the nearest integer.

Math.ceil(3.14159265)    // returns 4
Math.floor(3.14159265)   // returns 3
Math.round(3.14159265) // returns 3

To find the exponent of a number use the exp() function.

Math.exp(3.14159265) // returns 23.140692549708973

The log() method returns the natural logarithm (base E) of a number.