PHP

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.

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.

To redirect the current page to a different location you use the header() function in the following way:

header("http://www.hashbangcode.com");

You can use this function when you want to point the user to a different page. If you are writing a login script then this function would be useful to show the user a certain page depending on them entering the correct user information.

When printing off source code there is a handy function that will parse the code and produce nice looking syntax highlighted code. There are actually two functions you can use. The highlight_string() function takes a string as a parameter and will print the highlighted code. The highlight_file() function takes a file name as a parameter, the contents of which are printed off with highlighted syntax. For now I will concentrate on the highlight_string() function, but the output of these two functions is the same.

To use the highlight_string() function just pass it a string. The following code:

highlight_string('<?php 
function checkslash($slashes_string){
  if (get_magic_quotes_gpc()==1) {
    return $slashes_string;
  }else{
    return addslashes($slashes_string);
  };
};
?>');

Will produce the following output:

If you are querying a database you should get into the habit of sanitising your input, even if it's not coming from users at the moment it might do in the future. SQL injection attacks are all too common and they can be easily prevented.

The addslashes() function takes a string as the input and returns a string with backslashes before all characters that required quoting in database queries. The characters it acts on are quote, double quote, backslash and NUL (or a NULL byte). Magic quotes runs addslashes() on all COOKIE, GET and POST data. The important thing is not to use addslashes() and magic quotes on the same string as everything will be double escaped.

Use the get_magic_quotes_gpc() function to see if magic quotes is enabled. If it isn't then use the PHP function addslashes() to do the same thing. Use this function if you have any user input in order to sanitise anything that you are about to send to a database.

Those of you who have coded in PHP must have looked at the PHP website at some point, even if it was just to down load the latest version, or to look up a function reference.

What most people don't realise is that there is a really easy way to go straight to the page that you want without having to mess around with the tetchy search engine on the PHP site.

Lets say you wanted to know about the function phpinfo(). This is a debugging function that displays everything you could possible imagine about the PHP environment and is usually used by people who are just starting out with the language as it prints a lot of stuff to the screen.

To look at the reference for the phpinfo() function you could go to the following URL.

The following mode function will return the most commonly occurring value from an array of values, also called the mode. If just the array is used then only the most commonly occurring value will be returned. The second parameter can be used to return an array containing the mode and the number of times that this value occurs in the array.