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PHP 5 Class Constants

Class Constants

Class constant is a special identifier that hold fixed values throughout the running of your PHP script. To create a class constant, use the keyword const followed by the property name (without $ sign), as shown below:

Use of class constant

Class constant is usually used for the configuration value like the database user name.

Syntax

Class Student
{
const MXIMUM_MARKS = 100;
}
C

It is a convention to all class const must be in uppercase letter.


You can access class constant by using the scope resolution operator (::) same as static properties.

MyClass::staticConstant;

PHP class constant example

<?php

class Login
{
    const Login_NAME = "John Doe";
    const PASSWORD = "Admin123";
}

echo "User name: " . Login::Login_NAME."
"; echo "Password: " . Login::PASSWORD."
"; ?>

Output

User name: John Doe
Password: Admin123

In the Login class, Login_NAME and PASSWORD are the class constant. You can easily access with the help of scope resolution operator, as shown above.

Example

<?php

class Computer 
{
	const NAME = "Sony Vaio";
 
	public function display()
	 {
		echo " Name of Compuer Brand : " . Computer::NAME;
	 }
 
}
 
$obj = new Computer();
$obj->display();

?>

Output

Name of Compuer Brand : Sony Vaio

Example of class constant

The below example demonstrates the ability of accessing a constant within the class and outside the class.

<?php

class Student 
{
const ROLL = 38;
public $fi_name;
 
function Student($fi_name1)
{
    $this->fi_name=$fi_name1;
 
}
 
function display()
{
echo "Name of Student=". $this->fi_name."
"; echo "Roll no =". Student::ROLL; } } $s=new Student("Umar"); $s->display(); echo "
Outside the display method :"; echo "
Roll no =". Student::ROLL; ?>

Output

Name of Student=Umar
RoLL no =38
Outside the display method :
RoLL no =38

You can easily access class constant within the class and outside the class using the class name, as shown above.

Download Source Script


.

Class constant is very useful whenever you want to define fixed value throughout the class.


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