PHP Constants

Constants are fixed that once they are defined they cannot be changed .

Constants are name or identifier that can't be changed during the execution of the script.

Rules:

It can be started with letter or underscore only.

PHP constants should be defined in uppercase letters

It can be defined by 2 ways:

Using define () function

Using const keyword

define()

Syntax:

    define(name, value, case-insensitive)  

name: specifies the constant name

value: specifies the constant value

case-insensitive: Default value is false. By default it is case sensitive.

Example 1:

     <?php  

      define("MSG","LearningPoint92");  

        echo MSG;  

       ?>  

Output:

LearningPoint92

Example 2:

        <?php  

        define("MSG","LearningPoint92",true);//not case sensitive  

        echo msg;  

    ?>  

Output:

LearningPoint92

 Example 3:

     <?php  

    define("MSG","LearningPoint92",false);//case sensitive (It provides error)

    echo msg;  

     ?>  

    Output:

     error

Notice: Use of undefined constant msg - assumed 'msg'.

const keyword

const keyword defines constants at compile time.

It is always case sensitive.

Example:

 <?php  

const MSG="LearningPoint92";  

     echo MSG;  

        ?>  

Output:

LearningPoint92