Use of define() function in PHP

Use of define() function is to set a constant. It has three parameters: first is name of the constant, second is value for the constant and third parameter for constant name should be case-insensitive.

1) Following example is case-sensitive constant name:

Output:

This is value of MYCONST

Source Code:

<?php
    define("MYCONST","This is value of MYCONST");
    echo MYCONST;
?>

2) Following example is case-insensitive constant name:

Output:

 This is value of MYCONST

Source Code:

<?php
    define("MYCONST","This is value of MYCONST",true);
    echo myconst;  
?>