Introduction to PHP Programming

Introduction to Web Development

• PHP stands for Hypertext Preprocessor
• PHP is a server-side scripting language that can be embedded into HTML
• It appeared in the market in 1995, and the latest version is 7.4.0 (November 28, 2019)
• PHP is an object-oriented language that is interpreted and open-source
• PHP is platform-independent and can be used on Windows, Mac, Linux and Unix operating systems
• PHP is faster than ASP and JSP

Features of PHP

• PHP has a faster processing speed and better performance than other scripting languages
• It is open source, meaning it can be downloaded and used for free
• It has a clear syntax that is easy to understand
• It can be easily embedded into HTML tags and scripts
• PHP is a general-purpose language that supports MySQL, SQLite, ODBC and many other databases
• It is loosely-typed, which means that you don't need to declare data types for variables
• It has predefined error handling mechanisms
• PHP provides a high level of security
• PHP is compatible with various web servers such as Apache, Netscape, Microsoft, etc.
• PHP has a very large community with extensive documentation

PHP Fundamentals

• PHP code starts with an opening tag <?php and ends with a closing tag ?>
• PHP is partially case-sensitive. It is case-insensitive for keywords, user-defined functions, and class names
• PHP is case-sensitive for variables

Echo and Print

• echo is a language construct and a statement that can be used with or without parenthesis

• echo has no return value

• echo can pass multiple strings separated by a comma (,)

• echo is faster than the print statement

• print is a language construct and a statement that can be used with or without parenthesis

• print returns 1

• print cannot pass multiple strings

• print is slower than the echo statement

Statements

• Statements consist of one or more expressions
• Statements always end with a semicolon (;)
• Statements can be simple or compound
• Compound statements use curly brackets ({}) to mark a block of code

Whitespace and Line Breaks

• Whitespace and line breaks have no special meaning in PHP
• Whitespace and line breaks are equivalent to each other

Variables

• Variables start with a dollar sign ($)
• Variable names can contain alphanumeric characters and underscores
• Variable names should start with a letter or underscore
• Double dollar signs ($$) refer to a reference inside a variable

Constants

• There are two ways to define constants:
  • define() function: define(name, value, case-insensitive)
  • const keyword: const message = "1";
• echo constant() prints the value of a constant

Data Types

• Scalar (Pre-defined): contain a single value:
  • Boolean
  • Integer
  • Float
  • String
• Compound (User-defined): contain multiple values:
  • Array
  • Object
• Special Types:
  • Resource
  • Null

var_dump()

• Displays type and value
• var_dump() is a function that displays the data type and value of a variable

Comments

• Single-line comments: //
• Multi-line comments: /* */

PHP Operators

• Arithmetic: +, -, *, /, %, **
• Assignment: =, +=, -=, *=, /=, %=, **=, .=
• Bitwise: &, |, ^, ~, <<, >>
• Comparison: ==, !=, <, >, <=, >=, ===, !==
• Increment/Decrement: ++, --
• Logical: &&, ||, !
• String: .
• Array: [], array(), count(), in_array()
• Type: gettype(), isset(), empty(), unset(), is_array(), is_string(), is_int(), is_float(), is_bool(), is_null()
• Execution: include(), require(), include_once(), require_once()
• Error Control: @

Spaceship Operator

• Spaceship (<=>) operator returns:
  • -1 if less than
  • 0 if equal
  • 1 if greater than

Concatenation and Assignment

• .= concatenates two strings and assigns the result to the left-hand operand

PHP Control Structures

• If:
  • if (condition) { statement; }
• Else-if:
  • else if (condition) { statement; }
• If-else-if:
  • Combines if and else if
• Nested if:
  • An if statement inside another if statement
• Switch Statement:
  • switch (expression) { case value: statement; break; ... default: statement; }

Looping

• For Loop:
  • for (start; condition; increment) { statement; }
• While Loop:
  • while (expression) { statement; }
• Do-While Loop:
  • do { statement; } while (expression);

Jumping Statements

• Break:
  • Ends the loop
• Continue:
  • Skips the current iteration of the loop

Installing PHP

• Required Softwares
  • PHP
  • Web server that supports PHP (Apache)
  • Database server (MySQL)
• Installation Packages:
  • WAMP - Windows
  • LAMP - Linux
  • MAMP - Mac
  • SAMP - Solaris
  • FAMP - FreeBSD
  • XAMPP - Cross platform (Apache, MySQL, PHP, Perl)

XAMPP Control Panel

• Modules included: Apache, MySQL, FileZilla, Mercury, Tomcat

Two Main Applications of PHP

• Server-side Scripting:
  • Dynamic websites and web applications
• Command-Line Scripting:
  • Run PHP scripts from the command line for administrative tasks

Advantages of PHP

• Simple and easy to learn
• Fast
• Stable
• Open-source and free
• Large and supportive community