PHP Basics

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