PHP

Introduction
• PHP is a server scripting language, and a powerful
tool for making dynamic and interactive Web pages.
• PHP is a widely-used, free, and efficient alternative
to competitors such as Microsoft's ASP.
What is a PHP File?
• PHP files can contain text, HTML, CSS, JavaScript, and
PHP code
• PHP code are executed on the server, and the result
is returned to the browser as plain HTML
• PHP files have extension ".php"
What Can PHP Do?
• PHP can generate dynamic page content
• PHP can create, open, read, write, delete, and close files
on the server
• PHP can collect data
• PHP can send and receive cookies
• PHP can add, delete, modify data in your database
• PHP can be used to control user-access
• PHP can encrypt data

With PHP you are not limited to output HTML. You can output
images, PDF files, and even Flash movies. You can also output
any text, such as XHTML and XML.
Why PHP?
• PHP runs on various platforms (Windows, Linux,
Unix, Mac OS X, etc.)
• PHP is compatible with almost all servers used today
(Apache, IIS, Mercury, FileZilla, Tomcat etc.)
• PHP supports a wide range of databases
• PHP is free. Download it from the official PHP
resource: www.php.net
• PHP is easy to learn and runs efficiently on the server
side
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PHP Data Types
PHP 5 Syntax
• A PHP script is executed on the server, and the plain
HTML result is sent back to the browser.
• A PHP script can be placed anywhere in the
document.
• A PHP script starts with <?php and ends with ?>:
• A PHP file normally contains HTML tags, and some
PHP scripting code.
• PHP statements end with a semicolon (;).
PHP Case Sensitivity
• In PHP, all keywords (e.g. if, else, while, echo, etc.),
classes, functions, and user-defined functions are
NOT case-sensitive.
• All variable names are case-sensitive.
PHP Variables
• A variable can have a short name (like x and y) or
a more descriptive name (age, carname,
total_volume).
Rules for PHP variables:
– A variable starts with the $ sign, followed by the name of the
variable
– A variable name must start with a letter or the underscore
character
– A variable name cannot start with a number
– A variable name can only contain alpha-numeric characters and
underscores (A-z, 0-9, and _ )
– Variable names are case-sensitive ($age and $AGE are two
different variables)
PHP is a Loosely Typed Language

• We did not have to tell PHP which data type the

variable is.
• PHP automatically converts the variable to the
correct data type, depending on its value.
• In other languages such as C, C++, and Java, the
programmer must declare the name and type of the
variable before using it.
 PHP Variables Scope
• In PHP, variables can be declared anywhere in the script.
• The scope of a variable is the part of the script where the
variable can be referenced/used.
• PHP has three different variable scopes:
– local
– global
– static
Global and Local Scope
• A variable declared outside a function has a GLOBAL
SCOPE and can only be accessed outside a function:
Global and Local Scope
• A variable declared within a function has a LOCAL
SCOPE and can only be accessed within that
function:
PHP Data Types

• Variables can store data of different types, and different

data types can do different things.
• PHP supports the following data types:
– String
– Integer
– Float (floating point numbers - also called double)
– Boolean
– Array
– Object
– NULL
– Resource
PHP String
• A string is a sequence of characters, like "Hello
world!".
• A string can be any text inside quotes. You can
use single or double quotes:
PHP String
• The PHP strlen() function returns the length of a string.
• The PHP str_word_count() function counts the number of
words in a string:
• The PHP strrev() function reverses a string:
PHP String(Search For a Specific Text Within
a String)
• The PHP strpos() function searches for a specific text within a
string.
• If a match is found, the function returns the character position
of the first match. If no match is found, it will return FALSE.
• The example below searches for the text "world" in the string
"Hello world!":
Replace Text Within a String

• The PHP str_replace() function replaces some

characters with some other characters in a string.
• The example below replaces the text "world" with
"Dolly":
PHP Integer

• An integer data type is a non-decimal number

between -2,147,483,648 and 2,147,483,647.
• Rules for integers:
– An integer must have at least one digit
– An integer must not have a decimal point
– An integer can be either positive or negative
– Integers can be specified in three formats: decimal
(10-based), hexadecimal (16-based - prefixed with
0x) or octal (8-based - prefixed with 0)
PHP Integer
• In the following example $x is an integer. The PHP
var_dump() function returns the data type and value:
PHP Data Types
• A float (floating point number) is a number with a
decimal point or a number in exponential form.
• A Boolean represents two possible states: TRUE or
FALSE.
• An array stores multiple values in one single variable.
• Null is a special data type which can have only one
value: NULL.
PHP Object
• An object is a data type which stores data and information on how to
process that data.
• In PHP, an object must be explicitly declared.
• First we must declare a class of object. For this, we use the class keyword.
A class is a structure that can contain properties and methods:
PHP Resource

• The special resource type is not an actual data type.

It is the storing of a reference to functions and
resources external to PHP.
• A common example of using the resource data type
is a database call.
PHP Constants
• A constant is an identifier (name) for a simple value.
• The value cannot be changed during the script.
• A valid constant name starts with a letter or
underscore (no $ sign before the constant name).
• To create a constant, use the define() function.
• Constants are automatically global and can be used
across the entire script.
PHP Constants
• Syntax
– define(name, value, case-insensitive)
• Parameters:
– name: Specifies the name of the constant
– value: Specifies the value of the constant
– case-insensitive: Specifies whether the constant
name should be case-insensitive. Default is false
PHP Constants
• The example below creates a constant with
a case-sensitive name:

• The example below creates a constant with

a case-insensitive name:
PHP Operators
• Operators are used to perform operations on variables and
values.
• PHP divides the operators in the following groups:
– Arithmetic operators
– Assignment operators
– Comparison operators
– Increment/Decrement operators
– Logical operators
– String operators
– Array operators
PHP Arithmetic Operators
• The PHP arithmetic operators are used with numeric values to
perform common arithmetical operations, such as addition,
subtraction, multiplication etc.
PHP Assignment Operators
• The PHP assignment operators are used with numeric values
to write a value to a variable.
• The basic assignment operator in PHP is "=". It means that the
left operand gets set to the value of the assignment
expression on the right.
 PHP Conditional Statements
• Very often when you write code, you want to perform different
actions for different conditions. You can use conditional
statements in your code to do this.
• In PHP we have the following conditional statements:
– if statement - executes some code if one condition is true
– if...else statement - executes some code if a condition is true and
another code if that condition is false
– if...elseif....else statement - executes different codes for more than
two conditions
– switch statement - selects one of many blocks of code to be
executed
The PHP switch Statement
• Use the switch statement to select one of many blocks of
code to be executed.
PHP Loops
• Often when you write code, you want the same
block of code to run over and over again in a row.
Instead of adding several almost equal code-lines in
a script, we can use loops to perform a task like this.
• In PHP, we have the following looping statements:
– while - loops through a block of code as long as the specified
condition is true
– do...while - loops through a block of code once, and then
repeats the loop as long as the specified condition is true
– for - loops through a block of code a specified number of times
– foreach - loops through a block of code for each element in an
array
The PHP while Loop
• The while loop executes a block of code as long as the specified condition
is true.
The PHP do...while Loop
• The do...while loop will always execute the block of code once, it will then
check the condition, and repeat the loop while the specified condition is
true.
PHP Functions
• The real power of PHP comes from its functions; it has more
than 1000 built-in functions.
• Besides the built-in PHP functions, we can create our own
functions.
• A function is a block of statements that can be used
repeatedly in a program.
• A function will not execute immediately when a page loads.
• A function will be executed by a call to the function.
PHP Functions
• A function name can start with a letter or underscore (not a
number).
• Give the function a name that reflects what the function
does!
• Function names are NOT case-sensitive.
PHP Function Arguments
• Information can be passed to functions through arguments. An argument
is just like a variable.
• Arguments are specified after the function name, inside the parentheses.
You can add as many arguments as you want, just separate them with a
comma.