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PHP Tutorial

PHP Introduction

PHP 5 Installation

PHP 5 Syntax

PHP 5 Variables

PHP 5 echo and print Statements

PHP 5 Data Types

PHP 5 String Functions

PHP 5 Constants

PHP Arithmetic Operators

PHP 5 if...else...elseif Statements

PHP 5 switch Statement

PHP 5 while Loops

PHP 5 for Loops

PHP 5 Functions

PHP 5 Arrays

PHP 5 Sorting Arrays

PHP 5 Superglobals

PHP Forms

PHP 5 Form Handling

PHP 5 Form Validation

PHP 5 Forms - Required Fields

PHP 5 Forms E-mail /URL

PHP Form Complete

PHP Advanced

PHP 5 Multidimensional Arrays

PHP 5 Date and Time

PHP Include Files

PHP File Handling

PHP File Open/Read

PHP File Create/Write

PHP File Upload

PHP Cookies

PHP Sessions

PHP E-mail

PHP Secure E-mails

PHP Error Handling

PHP Exception Handling

PHP Filter

PHP Database

PHP MySQL Introduction

PHP MySQL Connect

PHP Create DB/Tables

PHP MySQL Insert Into

PHP MySQL Select

PHP MySQL Where

PHP Order By

PHP Update

PHP Delete

PHP ODBC

 

PHP 5 Data Types

String, Integer, Floating point numbers, Boolean, Array, Object, NULL.


PHP Strings

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:

Example

<?php 
$x = "Hello world!";
echo $x;
echo "<br>"; 
$x = 'Hello world!';
echo $x;
?>

PHP Integers

An integer is a number without decimals.

Rules for integers:

  • An integer must have at least one digit (0-9)
  • An integer cannot contain comma or blanks
  • 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)

In the following example we will test different numbers. The PHP var_dump() function returns the data type and value of variables:

Example

<?php 
$x = 5985;
var_dump($x);
echo "<br>"; 
$x = -345; // negative number 
var_dump($x);
echo "<br>"; 
$x = 0x8C; // hexadecimal number
var_dump($x);
echo "<br>";
$x = 047; // octal number
var_dump($x);
?>

PHP Floating Point Numbers

A floating point number is a number with a decimal point or a number in exponential form.

In the following example we will test different numbers. The PHP var_dump() function returns the data type and value of variables:

Example

<?php 
$x = 10.365;
var_dump($x);
echo "<br>"; 
$x = 2.4e3;
var_dump($x);
echo "<br>"; 
$x = 8E-5;
var_dump($x);
?>

PHP Booleans

Booleans can be either TRUE or FALSE.

$x=true;
$y=false;

Booleans are often used in conditional testing. You will learn more about conditional testing in a later chapter of this tutorial.


PHP Arrays

An array stores multiple values in one single variable.

In the following example we create an array, and then use the PHP var_dump() function to return the data type and value of the array:

Example

<?php 
$cars=array("Volvo","BMW","Toyota");
var_dump($cars);
?>

You will learn a lot more about arrays in later chapters of this tutorial.


PHP Objects

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.

We then define the data type in the object class, and then we use the data type in instances of that class:

Example

<?php
class Car
{
  var $color;
  function Car($color="green") {
    $this->color = $color;
  }
  function what_color() {
    return $this->color;
  }
}
?>

You will learn more about objects in a later chapter of this tutorial.


PHP NULL Value

The special NULL value represents that a variable has no value. NULL is the only possible value of data type NULL.

The NULL value identifies whether a variable is empty or not. Also useful to differentiate between the empty string and null values of databases.

Variables can be emptied by setting the value to NULL:

Example

<?php
$x="Hello world!";
$x=null;
var_dump($x);
?>