PHP for Beginners - Variables and Data types

Variables

Variable is nothing it is just name of the memory location.

Variable is simply a container.

Rules for Variable declaration

• Variables in PHP starts with a dollar($) sign, followed by the name of the variable.
• The variable name must begin with a letter or the underscore character.
• A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ )
• A variable name should not contain space.

Assigning Values to Variables

Assigning a value to a variable in PHP is quite easy, use the equality(=) symbol.

This assign value on the right side of the equation to the variable on the left.

A variable is created the moment you assign a value to it.

<?php
$city="Chennai";
$_city="Madhurai";
$city3="Tanjore";
?>

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 used.

In PHP we have three different variable scopes:

• Local
• Global
• Static

Local 

A variable declared within a function has a LOCAL SCOPE and can only be accessed within that function:

<?php 
function Test() 
{ 
$a = 7;
}
?>

Global

A variable declared outside a function has a GLOBAL SCOPE and can only be accessed outside a function. The global keyword is used to access a global variable from within a function:

<?php 
$a = 9;  //Global Variable 
function Test() 
{ 
$b = 7;
}
?>

Static

When a function is executed, all of its variables are deleted. But if you want any variable not to be deleted, the static keyword is used when you first declare the variable.

<?php 

function Test() 
{ 
static $b = 7;
$b++;
}

?>

Now that you have learnt about the Different Variables, let’s move ahead with the PHP Tutorial and have a look at the various PHP Data types.

Data types:

A variable can store different types of Data. Let’s have a look at some of the data types supported by PHP.

PHP Data types:

• String
• Integer
• Float
• Boolean
• Array
• Object
• NULL

String

A string is a sequence of characters. In PHP, you can write the string inside single or double quotes.

<?php
$city="Chennai";
$_city='tanjore';
var_dump($city); 
var_dump($_city);

?>

Here, PHP var_dump() function returns the data type and value.

Integer

An integer data type is a non-decimal number between -2,147,483,648 and 2,147,483,647. An integer must have at least one digit and can be either positive or negative.

?php
$mark=94;
$_mark=-5;
var_dump($mark);
var_dump($_mark);

?>

Float

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

<?php
$mark=94.65;
$_mark=-5.87;
var_dump($mark);
var_dump($_mark);

?>

PHP Boolean

A Boolean represents two possible states: TRUE or FALSE. They are often used in conditional testing.

<?php
$a = 10; 
$b = 20;
$c=$a>$b
var_dump($c);
?>

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. We need to declare a class of object using the class keyword.

<?php 

class Student 
{ 
function Student() 
{ 
$this->name = “XYZ”; 
} 
}
 
?>

PHP Array

An array stores multiple values in one single variable.

<?php 
$students = array(“Daniel”,”Josh”,”Sam”); 
var_dump($students); 
?>

Try it out yourself:

Step 1: Goto C:/XAMPP/ and run xampp-control.exe to open the Control Panel.

Step 2: Goto C:/XAMPP/htdocs/test then create a file "Variables.php". Inside this file Write the below scripts.

<?php
echo("Examples of Variables <br/>");
$city="Chennai";
$_city="Madhurai";
$city3="Tanjore";
echo("city =$city <br/>");
echo("_city=$_city <br/>");
echo("city3=$_city <br/><br/>");
echo("Examples of Local variables<br/>");
function Test() 
{ 
$a = 7;
echo("Local Variable a=$a<br/><br/>");
}
Test();
echo("Examples of Global variables<br/>");
$b=10;
function Test1() 
{ 
$c = 7;
echo("Local Variable c=$c<br/>");
}
Test1();
echo("Global Variable b=$b <br/><br/>");

echo("Examples of Static variables<br/>");
function Test2() 
{ 
static $a = 7;
echo("Static Variable a=$a<br/>");
$a=$a+1;
}
Test2();
Test2();
?>

Step 3: Open any browser and type https://localhost/test/Variables.php then see the output of the PHP Script.

Happy Learning !!!...

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PHP for Beginners

1. Introduction
2. How to install PHP?
3. How to run the PHP Script?
4. Variables and Data types