Signing up for PayPal Express Checkout

To work with PayPal digital goods you need to use PayPal Express Checkout system and then get the API credentials from the PayPal site.

Use the following link to sign up with PayPal :

Express Checkout sign up

You select the Express Checkout option and then either create a new account or convert your existing account into a Business account.

I have had some problems in converting an existing account to a Business account that will work with express checkout and I have found that the best way is to create a new PayPal account from scratch using the above link.

This sets up your account to work with Express Checkout.

Now you can get your signature details as follows :

Log into you PayPal account.

Click on the ‘Profile‘ tab.

Click on ‘My Selling Preferences‘ on the left hand side of the page.

For API Access, click on the ‘Update‘ link.

This takes you to the ‘API Access‘ page.

Click on ‘Request API credentials’ link and this takes you to the ‘Request API Credentials‘.

You need to select the ‘Request API signature’ so that you can obtain the three components of :

API Username
API password
API signature

Make sure that the Request API signature radio button is selected.

Then click on ‘Agree and Submit‘ button.

Copy all the details and store in a secure place on your PC.

Too many mySQL connections

If you have the situation in mySQL where there is the possibility of large number of connections, you can test for that specific error and then redirect to an different page :

<?php $link = mysql_connect("localhost", "mysql_user",
if (mysql_errno() == 1203) {
// 1203 == ER_TOO_MANY_USER_CONNECTIONS (mysqld_error.h)

Get auto-incremented value with PHP / mySQL

When you do an insert SQL statement which creates a new record, you often want to return the value of the auto-incremented field.

You can do this in PHP by:

$recid = mysql_insert_id(); //Return the number of the automatically incremented field after the insert statement

this is done after your mysql_query($sqlquery); statement

PayPal Mini Cart does not display

It is quite easy to implement PayPal Mini Cart on to your web site but there is a simple error that can stop the cart from displaying on your web page.

When you create you web page, make sure that the web page has proper validation at the top of the page such as

<!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Transitional//EN” “”>
<html xmlns=””>

Secondly, the Javascript code should be poistioned at the bottom of the web page just above the </body> tag.

Differences between PHP4 and PHP5

This listing of the differences between PHP4 and PHP 5 is is probably something that is quite common, but it is always worth a review.

PHP5 is a lot different than PHP4 with the main differences being in how it handles objects and classes.

Here are 10 major differences between PHP4 and PHP5 that you need to know:

1. Unified Constructors and Destructors:

In PHP4, constructors had same name as the class name. This used to cause overhead because every time you changed the class name, you had to change all the occurrences of that name.

In PHP5, you simply need to name your constructors as __construct(). (the word ‘construct’ prefixed by double underscores). Similarly you can name your destructors as __destruct(). (the word ‘destruct’ prefixed by double underscores.) In destructors, you can write code that will get executed when the object is destroyed.

2. Abstract Class:

PHP5 lets you declare a class as ‘Abstract’. (i.e. a class whose object cannot be created. You can only extend an abstract class) Also, a class must be defined as abstract if it contains any abstract methods. And those abstract methods must be defined within the class which extend that abstract class. You can include complete method definitions within the abstract methods of abstract class.

3. Final Keyword:

PHP5 allows you to declare a class or method as ‘Final’ now. You just need to use ‘final’ keyword that will indicate that the class cannot be inherited or the method cannot be overridden.

4. Exception Handling:

PHP5 has introduced ‘exceptions’. An exception is simply a kind of error and the ‘exception error’ can be handled in an exception object. By using an exception, one can gain more control over the simple trigger_error notices we were stuck with before.

When you are about to perform something ‘risky’ in your code, you can surround your code with a ‘try…catch’ block. First you surround your code in a ‘try {…….}’ block, then if an exception is thrown, your following ‘catch{……}’ block is there to intercept the error and handle it accordingly. You can write some PHP code in your ‘catch’ block which will get executed when an error occurs in the ‘try’ block. If there is no ‘catch’ block, a fatal error occurs.

5. E_STRICT Error Level:

PHP5 introduces new error level defined as ‘E_STRICT’ (value 2048). This error levels notifies you when you use depreciated PHP code. It is not included in E_ALL, if you wish to use this new level you must specify it explicitly.

6. Autoloading (the __autoload() function):

PHP5 introduces a special function called ‘__autoload()’ (the word ‘autoload’ prefixed by double underscores). This function allows you to avoid writing a long list of includes at the top of your script by defining them inside this function. So you can automatically load object files when PHP encounters a class that hasn’t been defined yet.


function __autoload ($class_name) {

include $class_name . ‘.php’;


7. Visibility:

In PHP5, class methods and properties now have ‘visibility’. There are 3 levels of visibilities:

Public: ‘Public’ is the most visible. Methods are accessible to everyone including objects outside the classes. And properties readable and writable by everyone including objects outside the classes.
Private: ‘Private’ makes class members only available to the class itself.
Protected: ‘Protected’ makes class members accessible to the class itself and any inherited class (subclass) as well as any parent classes.

PHP4′s method of declaring a variable as ‘var’ keyword is still supported in PHP5. The ‘var’ keyword is now a synonym for the ‘public’ keyword now.

8. Pass by Reference:

In PHP4, everything was passed by value, including objects. Whereas in PHP5, all objects are passed by reference. Take a look at this PHP4 code for example –

$peter = new Person();
$peter->sex = ’male’;

$maria = $peter;
$maria->sex = ’female’;

echo $peter->sex; // This will output ‘female’

As you can see in the code above, if you wanted to duplicate an object in PHP4, you simply copied it by assigning it to another variable (Pass by value). But now in PHP5 you must use the new ‘clone’ keyword. So the above PHP4 code, will now look like this in PHP5 –

$peter = new Person();
$maria = new Person();

$peter->sex = ’male’;

$maria = clone $peter;
$maria->sex = ’female’;

echo $peter->sex; // This will output ‘female’

9. Interfaces:

PHP5 introduces ‘interfaces’ . An interface defines the methods a class must implement. All the methods defined in an interface must be public. An interface helps you design common APIs. It is not designed as a blueprint for classes, but just a way to standardize a common API. A big advantage of using interfaces is that a class can implement any number of interfaces. You can still only ‘extend’ on parent class, but you can ‘implement’ an unlimited number of interfaces.

10. New Functions:

PHP5 introduces new functions which are not found in PHP4. You can find the list of these new functions in the PHP manual.

Simple example of a class in PHP

A simple example of a class in PHP
<?php # person

class person {

public function __construct( $name, $age, $height, $weight )
$this->name   = $name;
$this->age    = $age;
$this->height = $height;
$this->weight = $weight;

// functions that return information

public function get_name()
return $this->name;

public function get_age()
return $this->age;

public function get_height()
return $this->height;

public function get_weight()
return $this->weight();

// functions that change the object.

public function change_name( $name )
$this->name = $name;

public function add_weight( $weight )
$this->weight = $this->weight + $weight;

public function lose_weight( $weight )
$this->weight = $this->weight – $weight;


//Initialise a person
$paul = new person(‘Paul Gibbs’, 17, ‘6\’1″‘, 210);

$john = new person(‘John Smith’, 36, ‘5\”, 160);




echo(“Loose 10 pounds from this person<br/>”);





//A possible use :

$people = array($paul, $john);   //Create an array of people

foreach( $people as $person ) {
echo “This persons name is ” . $person->get_name() . “<br/>”;
echo “This person is “.$person->get_age().” years old.<br/>”;

class employee extends person {

public function __construct($name, $age, $height, $weight, $salary, $startdate)
parent::__construct($name, $age, $height, $weight);

$this->salary = $salary;
$this->startdate = $startdate;


public function get_salary()
return $this->salary;

public function get_startdate()
return $this->startdate;


$pete = new employee(‘Pete Coles’, 22, ‘6’, 200, 20000, 2012-06-04);




magic_quotes, addslashes(), and stripslashes() and PHP 6

magic_quotes_gpc, when on, automatically adds slashes to all GET/POST/COOKIE data so that you don’t need to use addslashes() before using GET/POST/COOKIE data in MySQL queries, etc. (e.g. with magic_quotes_gpc OR addslashes(), I’m becomes I\\’m). Well, magic_quotes_gpc is no convenience and just complicates things!

Since magic_quotes_gpc can be on or off, you don’t know whether to use addslashes() or not. You don’t want to use addslashes() when magic_quotes_gpc is on because you’ll add too many slashes (e.g. I’m becomes I\\\\’m), which is bad. Use addslashes() if magic_quotes_gpc is off, and don’t if it’s on (you can find out its setting with get_magic_quotes_gpc()). But you can’t use the same code all the time. One workaround is something such as:

if (!get_magic_quotes_gpc()) { $txt = addslashes($txt);

Using magic quotes has always been confusing and in PHP 6 they are apparantly going to remove it.  So it is better to program your scripts without using get_magic_quotes_gpc at all.