PHP Basics

Question 1

What is PHP?

Answer 1

HyPertext Preprocessor

A server side scripting language designed to interact with html

Interpreted by a scripting engine

Cross-platform, free and open source

Question 2

Is PHP a strongly typed language or a loosely typed language?

Answer 2

Loosely typed - you don’t need to specify whether a variable is an int, String etc. PHP figures it out from the value you assign it

Question 3

What are the rules for Variable names?

Answer 3

Always begin with $

Case Sensitive

Can include:

• letters
• numbers
• underscores

Can’t include
- spaces

Question 4

Which one can take multiple parameters - print or echo?

Answer 4

Echo

Question 5

What is a Constant?

Answer 5

Something that is set once and never changed

Question 6

What are the rules for defining Constant names

Answer 6

Don’t need to start with $

Convention is to use capital letters for variable

Set using define
- define(“CONSTANT_NAME”, value);

Question 7

What is the difference between Single quotation marks and Double quotation marks

Answer 7

Single:

• values will be treated LITERALLY
• escaped characters will be displayed exactly as typed

Double:

• values will be INTERPRETED
• escaped characters will have their represented values printed

Question 8

What does it mean to escape a character, and how do you do it?

Answer 8

It takes away any special meaning of the following character

Use \

Question 9

What does Type Casting mean, and how is it done in PHP?

Answer 9

Casting variables from one type to another

Normally done automatically in PHP:
$age_string = “18”;
$new_age = $age_string +1;

It knows that $new_age is an int not a string

Can be done manually:
$age_string = “21”;
$age_int = (int)$age_string;

Question 10

What is the difference between == and ===?

Answer 10

== means equal to (check if the values of the operands are equal or not)

=== means identical to (check if the values AND the types of the operands are the same)

Question 11

Are Arrays statically defined? Why/why not?

Answer 11

No

• You don’t need to know size in advance
• Can store any type of object in one array (eg can contain both int and String)
• Elements can be added or deleted at any time

Question 12

Which of the below is the correct way to define an array?

• $students = array();
• $students = array(“Ali”, “Mike”, “Lucy”, “Peter”);
• $students[] = “Faye”;

Answer 12

All of them!

Question 13

What are the three types of Arrays?

Answer 13

Enumerated
Associative
Multidimensional

Question 14

What is an enumerated array?

Answer 14

An array that is numerically indexed

If not specified, the first element is at index 0

Can set which position each element should occupy, e.g:
$students= array(1=>“ali”, 2=>“Mike”, 4=>“lucy”, 9=>“Peter”);

Question 15

What is an associative array?

Answer 15

An array that is indexed by strings

Specify a string instead of a number index within the square brackets

Each element can be referenced using the string index associated with the element

String index must be quoted

The string index is called the key

Creates a key/value pair

Question 16

What is a multidimensional array?

Answer 16

An array consisting of other arrays

Question 17

What are the rules for defining functions?

Answer 17

Must be within the php tags

Must begin with a letter or an underscore

Name must be unique

Can contain letters, numbers and underscores

Case-sensitive

Question 18

Where should you place function definitions?

Answer 18

At the top of a script or in separate files

Question 19

When should you use a function?

Answer 19

When you have code that might be executed in multiple places in the script

Question 20

What is a return statement?

Answer 20

They return a value to the statement that called the function

A function with no return statement implicitly returns NULL

Question 21

How do you call a function?

Answer 21

Writing the function’s name and parameter values in parentheses separated by commas

Question 22

What is auto-loading and why is it useful?

Answer 22

Allows you to keep scripts in separate files and then include them in the main PHP script

Entire contents of the included file is inserted in the calling script

Useful for defining functions needed by multiple pages

Question 23

What are the calling functions for including files?

Answer 23

include(“filename”) - if the file is not found, it produces a warning (E_WARNING) and the script will continue

require(“filename”) - will produce a fatal error (E_COMPILE_ERROR) and stop the script if the file is not found

Question 24

Should you include things that could be done in html within the php brackets?

Answer 24

No

Use PHP as little as possible

HTML takes less time to process than PHP