Chapter 5 - PHP Functions and Objects

Question 1

What are five benefits of using functions instead of contiguous, inline code?

Answer 1

• Involve less typing
• Reduce syntax and other programming errors
• Decrease the loading time of program files
• Decrease execution time, because each function is compiled only once, no matter how often you call it
• Accept arguments and can therefore be used for general as well as specific cases

Question 2

What does the ‘include’ statement do?

Answer 2

Using include, we can tell PHP to fetch a particular file and load all its contents. It’s as if you pasted the included file into the current file at the insertion point.

Question 3

What does the include_once statement do?

Answer 3

Each time you issue the include directive, it includes the requested file again, even if you’ve already inserted it. For instance, suppose that library.php contains a lot of useful functions, so you include it in your file, but also include another library that includes library.php. Through nesting, you’ve included library.php twice, by mistake.

Question 4

What does the include_once statement do?

Answer 4

Each time you issue the include directive, it includes the requested file again, even if you’ve already inserted it. For instance, suppose that library.php contains a lot of useful functions, so you include it in your file, but also include another library that includes library.php. Through nesting, you’ve included library.php twice, by mistake.

Question 5

What are require and require_once used for?

Answer 5

A potential problem with include and include_once is that PHP will only attempt to include the requested file. Program execution continues even if the file is not found.

When the file is essential to the program, it should be ‘required’. If the document is not fund, it will not run and will abort.

Question 6

What are require and require_once used for?

Answer 6

A potential problem with include and include_once is that PHP will only attempt to include the requested file. Program execution continues even if the file is not found.

When the file is essential to the program, it should be ‘required’. If the document is not fund, it will not run and will abort.

Question 7

How do you ensure PHP version compatibility?

Answer 7

PHP is an ongoing process of development, and there are multiple versions. If you need to check whether a particular function is available to your code, you can use the function_exists function, which checks all predefined and user-created functions.

Question 8

In terms of objects, what is a class?

Answer 8

When creating a program to use objects, you need to design a composite of data and code called a class.

Question 9

In terms of an object, what is an instance or occurrence of a class?

Answer 9

Each new object based on a class is called an instance.

Question 10

In terms of an object, what is an instance or occurrence of a class?

Answer 10

Each new object based on a class is called an instance.

Question 11

What are properties?

Answer 11

The data associated with an object.

Question 12

What are the functions used by an object?

Answer 12

Methods

Question 13

Give a example of declaring a class:

Question 14

How do you create an object?

Answer 14

$object = new User; $temp = new User(‘name’, ‘password’);

Question 15

What is a constructor?

Answer 15

When creating a new object, you can pass a list of arguments to the class being called. These are passed to a special method within the class, called the constructor, which initializes various properties.

Question 16

What is a constructor?

Answer 16

When creating a new object, you can pass a list of arguments to the class being called. These are passed to a special method within the class, called the constructor, which initializes various properties.

Question 17

What is the main benefit of using a function?

Answer 17

Using functions avoids the need to copy or rewrite similar code sections many times over by combining sets of statements together so that they can be called by a simple name.

Question 18

How many values can a function return?

Answer 18

By default, a function can return a single value. But by utilizing arrays, references and global variables, any number of values can be returned.

Question 19

What is the difference between accessing a variable by name and by reference?

Answer 19

When you reference a variable by name, such as by assigning its value to another variable or by passing its value to a function, its value is copied. The original does not change when the copy is changed. But if you reference a variable, only a pointer (or reference) to its value is used, so that a single value is referenced by more than one name. Changing the value of the reference will change the original as well.

Question 20

What is the meaning of scope in PHP?

Answer 20

Scope refers to which parts of a program can access a variable. For example, a variable of global scope can be accessed by all parts of a PHP program.

Question 21

How can you incorporate one PHP file within another?

Answer 21

To incorporate one file within another, you can use the include or require directives, or their safer variants, include_once and require_once.

Question 22

How is an object different from a function?

Answer 22

A function is a set of statements referenced by a name that can receive and return values. An object may contain zero or many functions (which are then called methods) as well as variables (which are called properties), all combined in a single unit.

Question 23

HOw o you create a new object in PHP?

Answer 23

To create a new object in PHP, use the new keyword like this: $object = new Class;

Question 24

What syntax would you use to create a subclass from an existing one?

Answer 24

To create a subclass, use the extends keyword with syntax such as this: class Subclass extends Parentclass …

Question 25

HOw can you call an initializing piece of code when an object is created?

Answer 25

To call a piece of initializing code when an object is created, create a constructor method called __construct within the class and place your code there.

Question 26

Why is it a good idea to explicitly declare properties within a class?

Answer 26

Explicitly declaring properties within a class is unnecessary, as they will be implicitly declared upon first use. But it is considered good practice as it helps with code readability and debugging, and is especially useful to other people who may have to maintain your code.