PHP Basics

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Questions and Answers

What is the purpose of the if...else statement?

To execute a block of code repeatedly

To select one of several blocks of code to be executed

To execute some code only if a specified condition is true

To execute different blocks of code based on multiple conditions (correct)

What is the syntax for the if statement?

if (condition) { code to be executed if condition is true; } else { code to be executed if condition is false; }

if condition then { code to be executed if condition is true; }

if (condition) { code to be executed if condition is true; } (correct)

if (condition) then { code to be executed if condition is true; }

What is the purpose of the switch statement?

To execute some code only if a specified condition is true

To select one of many blocks of code to be executed (correct)

To execute different blocks of code based on multiple conditions

To execute a block of code repeatedly

What is the effect of the expression $a += 5?

It increments the value of $a by 5 Signup and view all the answers

What is the purpose of the if...else if....else statement?

To execute different blocks of code based on multiple conditions Signup and view all the answers

In PHP, what is the purpose of the $ symbol in a variable name?

To denote a variable Signup and view all the answers

What is the output of the following code: <?php $t=date("H"); if ($t < 20) { echo "Have a good day!"; } else { echo "Have a good night!"; } ?>

Have a good day! Signup and view all the answers

What happens when you add a double to an integer in PHP?

The result will always be a double Signup and view all the answers

What is the purpose of arithmetic operations in PHP?

To perform mathematical operations on variables Signup and view all the answers

What is the purpose of the is_double() function in PHP?

To check if a variable is a double Signup and view all the answers

What is the purpose of concatenation in PHP?

To join strings into one Signup and view all the answers

What is the use of the \n escape sequence in PHP?

To insert a new line character Signup and view all the answers

In PHP, what happens when you try to use a string in an arithmetic expression?

The string is converted to a number up to the first non-numeric character Signup and view all the answers

What is the purpose of type casting in PHP?

To temporarily change the data type of a variable Signup and view all the answers

What is the use of the is_array() function in PHP?

To check if a variable is an array Signup and view all the answers

What is the purpose of the \t escape sequence in PHP?

To insert a horizontal tab Signup and view all the answers

What is the primary use of PHP in web development?

To generate dynamic web pages Signup and view all the answers

How are PHP scripts executed?

On the server-side by the web server Signup and view all the answers

What is the default file extension for PHP files?

.php Signup and view all the answers

What happens when a PHP script is accessed by a client's web browser?

The PHP code is executed on the server-side and the output is sent to the browser Signup and view all the answers

How are string literals defined in PHP?

Using single quotes and double quotes Signup and view all the answers

What is the purpose of variable interpolation in PHP?

To replace variables with their values Signup and view all the answers

What is the similarity between PHP and C/C++?

Syntax and paradigm Signup and view all the answers

What is the purpose of the reserved PHP tag?

To start a PHP script Signup and view all the answers

Study Notes

Arithmetic Operations

Subtraction: $a - $b
Multiplication: $a * $b
Division: $a / $b
Assignment operators: $a += 5 (also works for *= and /=)

Concatenation

Use a period to join strings into one

PHP Control Structures

Control structures: allow us to control the flow of execution through a program or script
Grouped into conditional (branching) structures (e.g. if/else) and repetition structures (e.g. while loops)

PHP Conditional Statements

if statement: executes some code only if a specified condition is true
if...else statement: executes some code if a condition is true and another code if the condition is false
if...else if....else statement: selects one of several blocks of code to be executed
switch statement: selects one of many blocks of code to be executed

The if Statement

Syntax: if (condition) { code to be executed if condition is true; }
Example: output "Have a good day!" if the current time is less than 20

The if...else Statement

Syntax: if (condition) { code to be executed if condition is true; } else { code to be executed if condition is false; }
Example: output "Have a good day!" if the current time is less than 20, and "Have a good night!" otherwise

PHP Details

Procedural language
C-like syntax: { } ;
Extensive Function Library
Good Web-server integration
Script embedded in HTML
Easy access to form data and output of HTML pages
Not fully object-oriented

PHP and HTML

HTML-embedded
PHP scripts are essentially HTML pages with the occasional section of PHP script
PHP script is enclosed in the tag pair: <?php ?>

Variables

Creation of variables: variable names always start with $ sign
Rest of the variable name can contain alphanumeric, underscore, and hyphen
Example: $name = “abc”;, $age = 36;
PHP is case sensitive

Escape Sequences in PHP

\n - Insert a new line character
\r - Carriage return
\t - Horizontal tab
\\ - Backslash
\$ - Dollar
\" - Double quote

Changing Data Type

Type casting process involves dynamically changing the type of data item
If we add a double to an integer, the result will be a double even if we are storing it in the original integer variable

Type Checking

is_array(var) - returns TRUE if the variable is an array
is_double(var) - returns TRUE if the variable is a double
is_float(var) - returns TRUE if the variable is a floating point number
is_int(var) - returns TRUE if the variable is an integer
is_string(var) - returns TRUE if the variable is a string
is_object(var) - returns TRUE if the variable is an object

What is PHP?

"PHP: Hypertext Preprocessor"
Open-source, server-side scripting language
Used to generate dynamic web-pages
PHP scripts reside between reserved PHP tags
Interpreted language, scripts are parsed at run-time rather than compiled beforehand
Executed on the server-side
Source-code not visible by client

What Can PHP Do?

Generate dynamic page content
Create, open, read, write, delete, and close files on the server
Collect form data
Send and receive cookies
Add, delete, modify data in your database
Control user-access
Encrypt data

What does PHP code look like?

Structurally similar to C/C++
Supports procedural and object-oriented paradigm (to some degree)
All PHP statements end with a semi-colon
Each PHP script must be enclosed in the reserved PHP tag

Comments in PHP

Standard C, C++, and shell comment symbols
// C++ and Java-style comment
# Shell-style comments

String Handling

String literals (constants) enclosed in double quotes “ ” or single quotes ‘ ’
Within “”, variables are replaced by their value: – called variable interpolation

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Description

Learn about basic PHP operations and control structures, including arithmetic operations, concatenation, and conditional statements.