PHP Comments

• There are two ways to use single line comments in PHP: // (C++ style) and # (Unix Shell style)
• PHP also supports multi-line comments, which are enclosed within /* and */

PHP Control Statements

• PHP if-else statement is used to test a condition and execute different blocks of code based on the condition
• There are various ways to use if statements in PHP: if, if-else, if-else-if, and nested if
• The syntax for an if statement is if (condition) { code to be executed }
• The syntax for an if-else statement is if (condition) { code to be executed if true } else { code to be executed if false }
• PHP also has a switch statement, which is used to execute one statement from multiple conditions
• The syntax for a switch statement is switch (expression) { case value1: code to be executed; break; ... default: code to be executed if all cases are not matched; }

PHP Loops

• PHP has several types of loops: for, foreach, and while
• The for loop is used to execute a block of code for a specified number of times
• The syntax for a for loop is for (initialization; condition; increment/decrement) { code to be executed }
• PHP also supports nested for loops
• The foreach loop is used to traverse array elements
• PHP has a foreach loop for arrays, which is used to traverse array elements

PHP Functions

• PHP allows you to declare and call user-defined functions easily
• The syntax for declaring a user-defined function is function functionname() { code to be executed }
• PHP functions support arguments, which are passed to the function when it is called
• PHP supports call by value, call by reference, default argument values, and variable-length argument lists
• PHP parameterized functions are functions with parameters

PHP Arrays

• PHP has two types of arrays: indexed arrays and associative arrays
• Indexed arrays are represented by an index number, which starts from 0
• Indexed arrays can store numbers, strings, or any object
• Associative arrays are represented by a key-value pair
• PHP provides the count() function, which returns the length of an array
• You can easily traverse an array in PHP using a foreach loop

PHP Math Functions

• PHP has several math functions, including dechex(), decoct(), base_convert(), and bindec()
• The dechex() function converts a decimal number to a hexadecimal number
• The decoct() function converts a decimal number to an octal number
• The base_convert() function converts a number from one base to another
• The bindec() function converts a binary number to a decimal number

PHP Echo

• Prints a string
• Can print multi-line strings
• Escapes characters
• Can print variable values

PHP Print

• Similar to PHP echo
• Always returns 1
• Syntax: int print(string $arg)
• Can print strings, multi-line strings, escaping characters, and variables

PHP Variables

• A variable is a name of a memory location that holds data
• Supports 8 primitive data types:
• Scalar Types: boolean, integer, float, string
• Compound Types: array, object
• Special Types: resource, NULL

PHP Data Types

• Scalar Types:
  • boolean
  • integer
  • float
  • string
• Compound Types:
  • array
  • object
• Special Types:
  • resource
  • NULL

PHP Operators

• Can be categorized into:
• Arithmetic Operators
• Comparison Operators
• Bitwise Operators
• Logical Operators
• String Operators
• Incrementing/Decrementing Operators
• Array Operators
• Type Operators
• Execution Operators
• Error Control Operators
• Assignment Operators
• Can also be categorized into:
• Unary Operators (works on single operands)
• Binary Operators (works on two operands)
• Ternary Operators (works on three operands)

PHP Comments

• Used to describe code
• Can be single-line or multi-line
• Helps other developers understand the code

PHP Switch

• Used for decision-making
• Syntax: switch (expression) { case value: code; break; ... default: code; }

PHP Loops

• PHP For Loop:
  • Used to traverse a set of code for a specified number of times
  • Syntax: for (initialization; condition; increment/decrement) { code to be executed }
• PHP Nested For Loop:
  • Used for inner or nested for loops
  • Inner for loop is executed fully for one outer for loop
• PHP For Each Loop:
  • Used to traverse array elements
  • Syntax: foreach ($array as $var) { code to be executed }
• PHP While Loop:
  • Used to traverse a set of code
  • Syntax: while (condition) { code to be executed }
• PHP Nested While Loop:
  • Used for inner or nested while loops
  • Inner while loop is executed fully for one outer while loop
• PHP Do While Loop:
  • Used to traverse a set of code like while loop
  • Syntax: do { code to be executed } while (condition)

PHP Array Functions

• PHP array() function:
  • Creates and returns an array
  • Allows creation of indexed, associative, and multidimensional arrays
• PHP array_change_key_case() function:
  • Changes the case of all keys in an array
  • Syntax: array array_change_key_case ( array $array [, int $case = CASE_LOWER ] )
• PHP array_chunk() function:
  • Splits an array into chunks
  • Divides an array into many parts

Introduction to PHP

• PHP stands for HyperText Preprocessor
• It's an interpreted language, no compilation is needed
• PHP is a server-side scripting language
• PHP is faster than other scripting languages like ASP and JSP

PHP Examples

• PHP files must be saved with a .php extension
• A simple PHP example is shown with a hello.php file
• Output of the example: "Hello by PHP"

Web Development

• PHP is widely used in web development
• Dynamic websites can be developed using PHP
• Basic knowledge of HTML, CSS, JavaScript, AJAX, XML, and JSON is required for web development

PHP Echo

• echo is a language construct in PHP
• It's used to print strings, multi-line strings, escaping characters, and variable values
• Examples of echo usage are shown in echo1.php, echo2.php, and echo3.php files
• Output of examples: "Hello by PHP echo", "Hello by PHP echo this is multi line text printed by PHP echo statement", and "Hello escape "sequence" characters"

PHP Print

• print is a language construct in PHP
• It's used to print strings, multi-line strings, escaping characters, and variable values
• Unlike echo, print always returns 1
• Examples of print usage are shown in print1.php, print2.php, and print3.php files
• Output of examples: "Hello by PHP print Hello by PHP print()", "Hello by PHP print this is multi line text printed by PHP print statement", and "Hello escape "sequence" characters by PHP print"

PHP Variables

• A variable in PHP is a name of memory location that holds data
• PHP do-while loop is guaranteed to run at least once
• Syntax of PHP do-while loop: do { //code to be executed } while (condition);

PHP Break

• The break statement breaks the execution of current for, while, do-while, switch, and for-each loop
• If used inside an inner loop, it breaks the execution of the inner loop only
• Syntax of PHP break: jump statement; break;

PHP Functions

• A PHP function is a piece of code that can be reused many times
• It can take input as an argument list and return a value
• There are thousands of built-in functions in PHP
• Advantages of PHP functions: code reusability
• Examples of PHP functions: strtolower(), strtoupper(), ucfirst(), lcfirst(), ucwords(), and strrev()

PHP String Functions

• strtolower() function returns a string in lowercase letters
• strtoupper() function returns a string in uppercase letters
• ucfirst() function returns a string converting the first character into uppercase
• lcfirst() function returns a string converting the first character into lowercase
• ucwords() function returns a string converting the first character of each word into uppercase
• strrev() function returns a reversed string

PHP Math

• PHP provides many predefined math constants and functions
• Math functions: abs(), ceil(), floor(), sqrt(), decbin(), and dechex()
• abs() function returns the absolute value of a given number
• ceil() function rounds fractions up
• floor() function rounds fractions down
• sqrt() function returns the square root of a given argument
• decbin() function converts a decimal number into binary
• dechex() function converts a decimal number into hexadecimal

PHP Data Types

• PHP supports 8 primitive data types, categorized into 3 types: Scalar, Compound, and Special.
• Scalar types: 4 types - boolean, integer, float, and string.
• Compound types: 2 types - array and object.
• Special types: 2 types - resource and NULL.

PHP Operators

• PHP operators are symbols used to perform operations on operands.
• Categorized into 10 forms: Arithmetic, Comparison, Bitwise, Logical, String, Incrementing/Decrementing, Array, Type, Execution, and Error Control.
• Operators can also be categorized into 3 forms based on the number of operands: Unary, Binary, and Ternary.

PHP Comments

• PHP comments are used to describe code or hide code.
• Supports single line and multi-line comments.
• Single line comments: 2 ways to use - // (C++ style) and # (Unix Shell style).
• Multi-line comments: enclose all lines within /* */.

PHP Control Statements

• PHP if-else statement: used to test conditions, with various forms - if, if-else, if-else-if, and nested if.
• PHP switch statement: used to execute one statement from multiple conditions, similar to if-else-if statement.

PHP Arrays

• Associative array: a type of array that uses strings as keys.
• Two ways to define associative array: using the array() function or by assigning each key-value pair separately.
• PHP Multidimensional array: an array of arrays, used to store tabular data.

PHP Math

• PHP provides many predefined math constants and functions.
• Math functions: abs(), ceil(), floor(), sqrt(), decbin(), and dechex().

PHP Include File

• PHP allows you to include files to reuse page content.
• Two ways to include files: include and require.
• Advantage: code reusability.
• include vs require: include allows the script to continue if the file is missing, while require halts the script with a fatal error.